Is there no way to designate in a settlement which house/shack/bed is mine?

First thing I do when I start is build myself a little hut, bed, and storage container, in the first area that it becomes a possibility.

Fast forward maybe 2 hours later after I progress past a certain point, and suddenly a bunch of nobodies move in and are helping themselves to my shack, requesting I rebuild for them. Even after setting up a separate area that I'd hoped they'd all sleep in and use, I always come back to the same lady hanging out in mine.

Is there no way to set ownership at all, or manipulate the AI in some way to ignore my stuff?

I understand your point entirely.

I'm trying to adjust my post-apocalyptic concepts of privacy.

So long as I plop a few extra beds around, they space out a bit.

they do rather take over though don't they

In Sanctuary, I built myself a two story home... first floor, crafting tables and storage, second floor is my bed, a table and some chairs, a toilet, a bathtub, etc. etc.. My Emma... she woke up and there was another woman in her bed, with another one standing right by her and a guy who was walking down the stairs... she felt so violated

Yeah, I'm not really liking not being able to designate a plot of land for yourself in settlements.

Might be a solution !

You can assign a settler to a bed.

In workshop view: Look at the settler, press 'command' - run to the bed - press 'assign'.

I assigned all the settlers to other beds (not mine).

Had a nap to midnight.

3/5 are in the assigned beds, the others on guard duty.

Might not apply to companions, but this could be worth testing.

You're a beautiful person

And here I thought I'd need to build a minefield in my own house. Can't wait till I get my copy tomorrow.