When the add/subtract option is selected: the mode changes, however this only reflects on the interface (the subtract toggle doesn’t change) after the first interaction.
When the smoothing option is selected: nothing seems to happen.
@stephomi I have a 2nd gen pencil and would be happy to test if you start a TestFlight program (apple’s beta testing solution).
See this answer for Apple double tap.
For TestFlight I closed it when I did the first release.
For now I don’t plan on reopening it (same as Android).
Maintaining several version on different platforms is a lot of work (single-man project), especially if I release the desktop version as well.
I might reopen it in the future, probably just for iOS though.
@stephomi apropos, can we expect a desktop version sometime soon?
Nope, I’ll probably do it at some point but not soon.