Selecting multiple objects to edit

I’ve been editing houses and just found out about the squaring feature. How can I mass select all the houses in a particular area to square the corners all at once?

In which editor?

Try click, then ctrl+click
or click, then shift+click

Those seem to work in every app I can think of.

If you answer the previous question, you can get a better answer.

In JOSM you may want to use search (Strg+F)
type:way and building=* and modified

edit: simplify search

Also in JOSM load the area,
Edit , Search , enter user:Sentinelprimek type:way building=* , Tools , Orthogonalize Shape
It takes about a minute to do those, then zoom around each row to fix the ones that are not meant to be right-angles.

(only selects those where you were the last editor)

In the standard web editor (named iD) it is not possible to select multiple objects.