Supposedly you can assign settlers to beds. How do you do this? And can you do it with the named settlers?

You do it like you assign anything else. In workshop mode, hover over the settler, named or otherwise, then hit 'Go'. Move the player to the bed in question, hover over it and hit 'Assign.' I play on a controller, so both actions are the 'A' button. Sadly, outside of workshop mode, there is little to indicate whose bed is whose. Within workshop mode, the bed will have a red or green icon depending on if it is used. But there seems to be no differentiation between player assigned beds and auto assigned. I wish we could change the names of the generic settlers so we could use the name as a sort of defining word to describe where they slept or what assignments they had. To me, it get tough as the settlement grows to know who's sleeping where and who can handle an extra assignment. Can't wait for a mod to fix that.

It doesn't look like you can assign the named settlers to beds.

I've heard that you can give each settler unique clothes to wear, that would help you identify them.