When in Workspace Settings you can use the arrow keys to increase or decrease the number of workspaces.
Keypad doesn't work.
4.11.1 (revision 2b800f4)
Created attachment 5385
make workspace_count_spinbutton editable
I personally think that this is a design decision and that this is rightfully so. Who on earth would *need* to increase their amount of workspaces by so much that they'd need to type in there? Don't forget: updating this setting takes effect immediately so typing e.g. a few numbers to many (instead of going for "11" you go for "111" or even "1111") ends up creating all those workspaces on the fly.
So I think it's actually safer to just increase the value step by step. Whoever wants to bump their workspace amount to an insanely high number (which would take too much time with the spinbuttons) can do so via xfconf-query or even via the GUI of xfce4-settings-editor.
That's fine - I can understand the logic in that. Not being privy to design decisions, if something works one day then doesn't work the next - then it's a bug to me ;)
Just another small note: GtkSpinButtons are editable by default, so this setting was indeed changed consciously (and hence most likely purposefully). The best explanation that I can come up with is the one I gave earlier (obviously it wasn't me who took that decision).
Hopefully noone else than elfy noticed this regression of sorts. I'm closing the report as WONTFIX since we don't plan to do anything.