Not sure which timer you're using, but it most likely will have an option to allow global hotkeys to split without focus. Livesplit for sure has this functionality, and I think it has some pretty decent autosplitter stuff going for it as well. I know some people were messing around with a newer visual autosplitter, so I'll bump this thread to discord and see if anyone made progress with that.

And here's my 1.0 US cart. Hard to make out here, but it has the number 23 stamped just below the Mario Zone statue.

here's a pic of my 1.2 JP cart. 23 B stamped towards the bottom right.

Are you just looking for blank splits? If so, that's easy enough. Any% Glitchless, I'm guessing?

Also, if you have any questions, feel free to drop by the SML2 discord: https://discord.gg/TxATRKV