Is it possible to repeat a macro, or is that illegal?

[Stepjam]

Breaking TOS isn't illegal it's a private agreement between 2 parties not legally binding. Ie se only action is to cancel your account. This is different from a licensed like your os.
But yes it would be against TOS and could get your account banned.

Eh, when people say illegal in contexts like this, it's understood they don't mean illegal as in you'll go to jail. It's just illegal in that you can get banned. It's sorta like saying that touching the ball with your hands in soccer is illegal if you aren't the goalie. Obviously cops aren't gonna storm the field if you do so.

[Canadane]

You won’t go to jail but you might go to gaol.

[SamSmoot]

Hitting Synthesize and the macro button is kind of tedious, so I was wondering if there's a way to repeat that process? If not, is it legal to make a local macro that does this?

I position my current macro button on the top, mostly empty bar, then put the synth button right on top of it. Also, put a 2 second delay at the start of the macro so you don't start running commands before the synth is ready if you click the macro too soon.
Then, I just position the cursor on synth, click twice, and do something else while it completes.{