If I changed jobs which job should I show in "My Occupation box?

Just enter your most recent (or current) occupation.

The occupation that you enter on your tax return doesn't have any effect on your taxes or the processing of your tax return.

If it doesn't have any effect, why is it being requested? I'm in a similar situation. I am transitioning to a new profession so technically I could list <old but still current> profession, <new> profession (working in internship), and student < part-time, post 4-year degree in a certificate program for which I have received a tax form as potentially eligible for a credit but haven't gotten to the point where TT asks about this>.

JohnW is correct that it does not affect your return or its processing. However, an auditor may look at the occupation and use that to see if the expenses being claimed are reasonable and necessary for that occupation. For the average person, it really won't matter.

@lilly54 

While I hope not to meet my first auditor this year (or any year), since that might be the case, what do I put?

Personally, I like student. It is amazing what all things a student can get into and covers a wide variety of things. Since you are one, that would be my choice.