Is there any way to incorporate blank measures?
Do you mean a “rest” or “no chord” measure? Use the “FX” menu at the bottom of the song editor:
The “Rest” option tells Strum Machine to do nothing on that beat. Note, often you’ll want to start a period of “silence” with either a “Stop” or a “Diamond”, to instruct Strum Machine to either mute the strings entirely or let them ring out before the period of rest.
Beaumont Rag and Theme Time are a couple examples where you can see this in practice.