How to debug scheduled transaction with formula?

[Roman Starkov]

I've created a scheduled transaction that uses a formula to calculate 
the amounts, and after running it once it turned out the formula was 
slightly off.

So I deleted the wrong instance and tried to re-run the scheduled 
transaction. But I couldn't find any way to re-run it - it seems that 
there isn't any UI to reset the "last occur" date back to "never", nor 
to force a re-run of the previous occurrence.

What options do I have other than creating a completely new SX for every 
iteration of debugging?

(version 2.2.9)

Thanks!
Roman