Currently number string frequency and length are not controllable, there's only an on/off switch. Same for punctuation but for punctuation it would also be nice to be able to control what punctuation characters are able to appear. Preferably as writable list like {[()]}*!=?&.,_:;~'|<>^ if that's not too hard to implement.
I've recently setup additional keylayers commonly used on 40% keyboards so I'm able to type numbers and special characters without leaving the letter keys, this looks like a good offline trainer for learning those layers which is usable even on a shittop but its numbers and special characters are far too sparse for my preferences and I feel like I'm wasting time writing regular words too much.