@Perkin
I am in the group that hates doing things like that (changes via CLI) wearing blinders.
I like having to stare at what I am about to make changes to
before they get done. I have been known to (more frequent than I like) select the wrong file(s)
There are other tricks for a
quick load.
Place all fonts to be used into a folder along with the a (matching @fonts)stylesheet., When you use 'Add Existing', just select All in that folder.
Wham Bang they are done.
select (X)HTML files in the book: right-click; Link stylesheets
select all stylesheets that will be used in those file (note that any existing stylesheet links will be deleted in those files).