Not sure I understand. Why not use the EQs in the outputs?

In that block diagram the original signals are all summed unfiltered and then go to the filter for the sub. That would be easily done with TM FX without any loopback. Just send any signal that goes to LRCLsRs also to the sub output.

this is a typical and very SPECIFIC 5.1 production issue. that i have also, of course .i will follow this topic.

edit : well this is no "issue", this is a procedure, in fact, to maintain consistency of the audio material through domestic broadcast sytems...

Ok. I will try to be clearer.
To use bass management in 5.1, you have to use the physical sub ouput (which is different to the lfe channel which come from the software) for both following groups of channels coming from the software :
1/ the 5 channels LRCLsRs which are low passed filtered at 80hz. So just the band 20 to 80hz of these channels are sent to the physical sub output (these channels are also sent to their respective physical outputs LRCLsRs and eq with a high pass at 80 hz
2/ the 0.1 channels (aka LFE) which is to be eq which a low pass at 120 hz.

I think the confusion comes from the fact that the sub and the lfe are completely different things.

The problem in TotalMix is that to low pass the LRCLsRs channels, the only solution is to apply an eq on the sub. Then by doing so we also low pass the lfe channel at 80hz whereas you want to low pass it at 120 hz

Hope it is clearer.

Thank you again.
Simon