First aid supplies and tools are out of scope of this question?
I think stocking things that will be useful/essential for growing/procuring food and water is a good way to go. And some sanitation supplies.
A large quantity of salt and some saltpetre for curing meat, line fishing supplies (hooks, swivels, line, sinkers), buckets with lids, pallet wrap, a roll of plain fencing wire. Disposable face masks and gloves. spare sunglasses and reading glasses. Lots of light rope. tubes of silicone and various plastics glues. Batteries. Pool chlorine. Shampoo/conditioner. Mouse traps.
Shampoo, dental floss, paper towel, disinfectant, razor blades, deodorant. Most of these are comfort items, but I stock them because if we bugout I want to maintain as much a sense of normality as possible. There will be enough stresses without the added annoyance of missing the comfort items we all take for granted.
Of course entertainment will be scant so ... some of the following: decent board games and puzzles, a few decks of cards, a guitar, some art supplies and a few types of sporting balls. A tub of lego for little kids.
Chap stick / Lip balm Sun Screen I bought my self both a straight razor and razor which takes reusable blades and a couple of hundred blades- still mostly use my disposable but every month or so I practice with the straight razor !! You mentioned underwear in OP but when spirts are down and you feel like shit, clean / new underwear and fresh socks makes you feel human again
For shelter mosquito nets and head nets often forgotten the flies will drive you mad after 3 days.
Desalination and water catch, barrels and buckets, I keep a few packets of cheap disposable lunch boxes to keep food in - it is feast and famine in the wild.
Food procurement (trapping wire, mouse traps, fishing, hunting etc) heirloom veg seed, small paint brushes to fertilise the veg if there are no bees
Moral as stated cards, note books, books etc.....
A key item mostly ignored in the bushcraft is a barometer for weather forecasting.
I read accounts of people who went into the wild and lives there for years and what they took with. Link below to a short account of a person who lived for 6 years on an deserted pacific island. He was there there for about a year then left and returned - read what he took on his second trip.