Is there a way to do a mass update to a memorized transaction? We want to make over 100 of them inactive.

I don't see Inactive as a supported transaction mass update field. You should be able to do this via CSV import, though

No CSV imports for Memorized Transactions though.

You trying to deactivate the memorized transaction definition? I think that requires scripting

Yes, it is that exactly. But googling I have gotten mixed results if that is possible or not through scripting.

Seems like it definitely can. SuiteScript Supported Records in NS Help Center

TY