Goto settings: madiface USB or ADI 2 DAC(the taskbar icon) go to "About" banner. Try "sort ASIO devices". I think this is for driver priority. Either choose lexicographical ascending or descending. I do this. Happy for other ideas

It has some limitations. Not very user friendly. I have the UCXII as master device, digiface plays through hardware I/O, only routing. The ADI2DAC connects to coax with the UCXII.

I have the UCX2 mostly connected to PC. Bought the digiface to get more inputs so the only output(from digiface) i use is connected to UCX2. I have cd players, bluray, recievers, DAB radio connected over Toslink. Use coax or tos to ADI2DAC. Not ur usual HIFI setup, but I love it. It works for me because I dont play 384khz or DSD files. In practical use 24/96 is more than enough, so USB from ADI2DAC is not in use pr today. Feeding the dac with spdif gives really good sound.

To the topic I do want to add that multi-interface works, but it could be done in a much sleeker way. First it should have a regular 3-way switch for asio device priority, get rid of that lexicographical nonsense.

Second; multi-interfaces should have better integration in TMfx. Like then u connect another device u just add more I/O to the same TMfx window.

For christmas I want a TMfx-like interface for ADI2DAC, all controls including 5 way graphical PEQ and knobs for loudness and b/t, upload to device and so on

@happy_amateur We are probably similar kind of users, I understand you setup. Do you use also ARC USB with your UCX2? If not I recommend it - very good device. Switching setups, nice muting, volume control much better then with DAC IR remote control, which has already bad contact on volume down after several months of use, I had to start use of my universal RC. ARC is really great thing for our purpose.
ADI2DAC does not have HW for TM, it a pity. Do not expect such Christmas present.

By the way yesterday I found another annoying limitation. Once other usb device is connected together with ADI2DAC, DAC has limited ASIO functionality to max PCM 192kHz by the driver. Player cannot play DXD or DoP DSD128 and DSD256 files. This is because the other device (for me Digiface USB) is limited to max 192 and driver is probably synchronizing clock across all devices and does not allow more even if the hw can do it.
Limitations and walls everywhere...:-(

@MC
There is probably some misunderstanding. I will try to describe it more.

HW :
Intel NUC 6 cores/12 threads at 4GHz, 16GB RAM, NVME disk, RME devices connected to USB3 ports, everything else thunderbolt. Windows 10 .
latest RME drivers
Digiface USB with ARC USB for TM
ADI-2 DAC FS
Neumann monitors KH750 DSP + KH80DSP front pair aligned by MA1 room correction SW
also some other analog hifi gear.

It is not studio use, just home use for playing video mch to WDM device and audio stereo directly to DAC via USB and audio MCH to DF and then 2 stereo dacs via toslink. Also stereo TV toslink to DF and then DAC. Another option is playing from DF directly to monitor KH750 via toslink to coax converter. Those setups easily switched in TM.

Simply - both DAC and DF are connected to PC via USB3 ports. And also toslink from DF to ADI2DAC and some other DAC for 4.0 playback. When playing stereo then DAC switched to USB input, when MCH then switched to toslink. Both dacs synchronized by DF internal clock when playing MCH.

Requirements:
Because I play also DXD and DSD 128 and 256 via DoP I need DAC connected also via USB. No way via DF, converting DSD to PCM introduces really lot of ultrasonic trash above 30kHz as seen for instance in Digicheck.
Also I need only ASIO for music playback because I need SR switching, each track can have different format and SR. This works with ADI2DAC via USB and ASIO only.
MCH is 4.0 output mixed in DF TotalMix.
I want to play stereo directly from Foobar via usb to DAC.
I want to play MCH from video player via WDM driver to DF. This is not a problem. Works.
I want to play MCH PCM from Foobar via ASIO to DF.

Problem:
There is only one logical ASIO device in the system - ASIO Madiface USB. Nothing else. Even if I have 2 USB devices connected. Which HW this logical device leads to is defined in driver settings About, Sort devices, Preview - the 1st one. The second is not accesible. Or is it? How?
When DAC is connected via USB - it becames the first one and I cannot play to DF. I have to switch the device order in About dialog.

How to play to different ASIO devices without changing parameters in the driver? Is there any way?

What is your recommended configuration which meets the requirements and works without manual reconnecting cables for each purpose?

Yes, I set 2 Channel Mappings in Foobar, I know about it. It is needed for MCH. I have now 2 ASIO configurations:
- STEREO with Analog 1 and 2 (DAC) Left and Right
- MULTICHANNEL with ADAT 1-8 (DF) L,R,C,Lfe,SL,SR,BL,BR

Two possibilities:
1. DAC is first in drivers About/Preview dialog:
When playing stereo track to stereo asio config - it goes to usb dac. Correct.
When playing stereo track to MCH asio config - it still goes to usb dac.
When playing MCH track to MCH asio config - front channels are still going to usb dac and all channel outputs from DF are distorted.

2. DF is first in driver About/Preview dialog:
When playing stereo track to stereo asio config - it goes to DF ADAT1,2 not correct
When playing stereo track to MCH asio config - it still goes to DF ADAT1,2
When playing MCH track to MCH asio config - front channels are going to ADAT 1,2,..... correct

Looks like Foobar ignores channel mappings? Looks like only order of physical devices is important, not their names. Maybe it is a bug in FB, I don't know. I am new in multichannel.

Another problem:
In TM I send DF playback inputs to ADAT 1-4 FL,FR,SL,SR. Physical SPDIF toslink connections are Out1 to first DAC for front channels, Out2 to second DAC for surround. All physical outputs set to SPDIF.
This works for SR 176 and 192. Output is to correct physical out - front Out1, surround Out2.
But for lower SR physical Out2 is silent thou in TM ADAT3-4 are live. Seems to me that for lower SR they are directed to Out 1 together with ADAT1-2 instead of  Out 2 even if channels are set as SPDIF and not ADAT.

Is it true? Is it possible to have fixed physical Outs for different sample rates? Or the only possibility is to resample everything to 176/192?

TM FX clearly shows you how ADAT S/MUX causes the collapsion of channels and thus re-routes those. There should be a simple workaround, though: If you add the routing to work at 44/48, then this routing will not interfere with the one needed for 192 kHz. Because those TM FX Hardware Output channels are not used from the SPDIF output in that moment

I promised to tell some finding about ASIO playback in Foobar. So here it is. I have done many different testing and studying and googling and I saw I am not alone with this problem.

If you need to playback only stereo you have no problem with Foobar ASIO. I also had no problem for really many years... until I strarted to try multichannel. Why? Its easy - Left and Right channels are hardcoded (preselected) for first two channels in row.

If you want more then you have to create separated channel mapping and use this virtual device as output. This also works. But FB does not remember this settings over restart, probably also after change of output device. Virtual device is still there but without previously selected mapping. If you want to change mapping you get error "No ASIO device found". Interesting is that mapping is stored in foo_out_asio.cfg file. But probably not read correctly or something like that.

There is some talk about this error on the net, it not new thing. Not many people experienced this error because not many people use FB for mch playback. Problem is that ASIO plugin is not maintained for many years.

So the only way for mch playback is to map channels after every FB start. And switching between different output HW by different ordering in RME driver setting.
Crazy. But probably no other workaround.

Great info about future possibility of SR changes, thank you very much. This will make life more simple and better selling point for hifi users.

Yes, I know JRiver, I have tried really many players on Windows and Linux during last 13 years. But FB is for me absolutely the best in possibility of configuration, plugins, speed, functionality - nothing can beat it. And there are only some players supporting Folder View. This is a must for me.
I have tried Jriver several times and had many terrible problems and user interface I really don't like. But now I probably use it more for video and TV tuner (this is also buggy). From sound point of view its mch mixer seems more muddy and indistinct localization comparing my own mixing in TM which is much cleaner. Night and day. Using its WDM driver I will investigate maybe for Tidal.