See https://skyline.ms/announcements/home/support/thread.view?rowId=59751 "PRM-PASEF method creation, 'All targets must have an ion mobility value' "

and related email thread between Brendan, Nick, and Brian 4/6/2023

There's the problem the user hit in method export, and also the problem of the value not showing up in the document grid for the target as one would intuitively expect. Per Brendan that ion mobility info should just be saved with other precursor info whenever there's a library change