You can enter any rhythm into PolyNome.
Tap on a Metronome and choose "Edit Pattern"
Then use the buttons at the bottom of the page to enter note groups.
You can edit note groups to remove some of the notes by tapping the "Edit" button.
As a shortcut, if you long press on a button, the note group will be entered and the Edit window will appear.
This video demonstrates entering a cascara pattern:
And this video demonstrates how you can program an entire snare solo, including flams, drags, diddles, etc.