Actually, there are! You can click below those buttons, where it says the name of the "brush," and it will bring up a full on-screen keyboard (looks like it was meant to be used on phones?) and you can type the name of the "brush" you want. There are some cool ones which seem less common than others? I found "Quicksand" and "Recurse", the latter of which I only saw once naturally, but I could deliberately re-invoke it and got a pretty neat effect in my opinion!
Yeah I plan to add lots of brushes with parameters so that feature can eventually be used to filter down the stochastic brushes and people can make “recipes” for one another to get interested in both painting and programming.
Right arrow selects the next brush. Left arrow cancels the effect of the current brush and selects another.
Yeah and spacebar opens the command prompt so you can type - with up and down arrows to pause and unpause.