Will we ever get an option to have script params as multi-select?

Unlikely I would wager. The same goes for workflow fields. Its easy enough to either have a JSON array in a text field or a single link to a saved search that defines the set that you want.

Comma separated list of internalids is fairly typical and simple.

That just sucks, have to fetch the internal IDs and make a comma separated list or go to a search and update it. Unnecessary 30 sec task.

You can use a custom record that holds your multi-select and other fields and have your script param reference that

30 seconds? wow you must have a huge dataset.

I am just lazy when it comes to stuff like this 😅. Currently have it as a saved search. But even loading the saved search and editing the filters before running the script is painful.

Just automate the setting of the parameter from another script using N/task