Not everything. I learned quite a bit from this exchange.
My takeaway is if I have a SS fee from a deadhead ticket to go home at the end of a trip (or to MEM to start a trip), I have two choices (that we know of, since I may not have found all the glitches )
1. Find a DH leg on my trip within 3 days of my SS fee and associate it with that.
2. If no DH leg like that available, then pick the first or last trip segment, accept there’s going to be the red warning message (most likely) and put an appropriate comment in my travel report. Hopefully it gets fixed by the auditor after submitting the report and doesn’t require an Insite.

Cheers