I've always wondered why I can't send companions here when I disband them. I've found the home plate as a more useful house than others (including places you build) because the market area is right next to you. But then I need to send my companions somewhere that I never go to or back to their home. I might just be dumb and there is a way to do this but if not, are there any mods for this yet.

that place can barely fit dogmeat

I wish for 2 things when it comes to dismissing companions.

1. Send them back to the original location you found them.

Is it just me who feels bad sending to one of my settlements when they might actually want to go home? Piper might want to return home to Nat. Absolutely sure of this after our talk when I told her not to ignore her sister and be a part of her life... and then I prevent her from going home. "Nah go to Covenant and hang out with all the other Companions I dismissed." Or maybe Hancock wants to return to duties as mayor of Goodneighbor? Or Macready wants to go back to the Third Rail and drink beer and listen to Magnolia?

2. Send them to Home Plate. Sure it is small but I won't lose a companion in there. Besides after the bartender of the Colonial Taphouse went missing, I sort of turned Homeplate into a bar with pool tables and such. It would be a nice relaxing place for them.

You can, but only if you haven't sent them some place else already. The first time you dismiss someone just back out instead of selecting a destination and they will return to the last place they were stationed (ie. the place you found them).