I could not get the shift-enter option to regenerate a new mansion from the same floor plan.
Does anything happen at all when you press shift+enter?
The trees moved and mostly disappeared when I toggled the decorations.
The whole scene (including trees) is recreated when you toggle decorations. Sometimes you get more of them, sometimes fewer. Try it several times to get the amount you need.
Generating a cellar or basement level... Style option for half-timbered buildings
That's on todo list.
Ability to add/delete entrances on the blueprint... Ability to generate a Grand Entrance on one side of the mansion
It's probably not too hard to mark entrances on the blueprint, I'll think about it. "Grand Entrance" is an interesting idea, but I'm not sure how it should look (taking style parameters into account".
Fireplaces generate connecting to the chimneys
And that is too hard. Right now chimneys are placed randomly on roofs, but I can't do the same with fireplaces, they would interfere with windows, passages, stairs etc.
Style option to generate a hobbit mansion like Bag End
Can't do it unfortunately (for many reasons). It would be interesting to see a multistorey hobbit mansion...