Way back in the day, I used to build interiors with t2 insolated wood.
With the foundations just a bit higher than the large chest, then I would place 6 chests and use a ceiling tile to cover them. The tile and the foundations looked the same, but a repair hammer would have given the whole thing away.
No one ever found my chests.
Very few raiders run around checking every single thing with a repair hammer.
Although if secret door’s were a thing it could cause more people to start.
I admit I haven’t been playing in a year, but misdirection always worked for me when I was playing.
I didn’t make it too difficult for them to get in, I would leave a few twigs and scraps, maybe an extra thrall or two. And they would scutter away like the vermin that is an off line raider.
I was never leveled and I kept my stuff, Just fooling them wasn’t fun though I wanted to retaliate.
It wasn’t until server transfers made escape possible that I took a break from PVP, then IRL made it a break from the entire game. I can’t devote the appropriate amount of time to do the game justice.
I think it could be done by making door that looks exactly like foundation / wall but opens like a door - that way people either have to check every single wall or just won’t find it.
That’s just one example and i think it would be neat