I wouldn't be so quick to blame the handoff person, sometimes you need to turn your back for a second and that's all it takes they cant be staring at the tips 24/7

You should definitely tell your SM that this is happening. An incident report should be filed every time anything is stolen, even if you don't see who did it.

Idea: Buy some dollar store fake money. Put it in the tip jar. Remove all actual tips the second the customer leaves into a tip bag behind the counter near the safe.

We do this at my store. Too many grab and dashes. Some jerks will stare you in the eyes and grab a fistful without breaking eye contact. Enjoy your Hollywood money! Just make sure it's clearly marked and your tip people know its fake. It just needs to look like real money at a glance to make people see it's a tip jar.

Try to make a homemade tip box people can’t stick their hands into. It’s not much but it helps in the tiniest bit

Why is it accessible for customers?

You cannot blame someone for doing their job.

It all boils down to - why is the tip jar there? Is it safe there? Clearly the answer is no as its been stolen twice. Why wasn't it moved after the first time?

I'm hearing a leadership issue, not a barista walking away issue.