An extremely obvious way to detail if a person has a will would be to give Mausoleum PCs an ability to wand players. When they die, a white fugue aura surrounds the body (it glows white).
No doubt this would mean messing with our notoriously quirky death system, so another method would be viable-
Much like the "take pack" item inside of a bag, place a "this PC has a will" item beside it, so it is always on the first page of the inventory.
Sorry, but a Will is simply not something that should (magically) stand out. It is more interesting if you can get people to actively look for these things on dead bodies anyway.
This might help with the unfortunate bug of all your written in game notes being erased when you enter the fugue. So... the obvious choice of writing a note and leaving it in your pack is diminished, though a will holder could likely use PM to tell them what they would have found before the bug.
There's now also the issue of logged out bodies having unyankable packs. This has made dying seemingly less stressful (to take a relaxing break after fugueing on a quest, makes death less harsh) and I enjoy that, but brings in these issues. Maybe only a dm can yank a pack of a logged out fugued person?
I'm also not sure if the fugue erasing bug effects notes written by the NPC scribes. This might be the best solution at the moment, if it does not as it does with the PC writing tablet.