Unfortunately this doesn't seem possible even with the advanced search feature. You'd expect to be able to find it under “Actions in microflows, nanoflows and rules” but there you can only search for create / delete / retrieve / etc. of particular entities, not for a specific type of action. It would be nice to have an option for this, might be worth posting on the ideas forum.
there’s an option where you can finde everything inside your App. in Edit – > Find Advanced…
However, I leave you this link here with more info:
I hope this can help you, best regards!
I am also trying to do the same in 9.12.8 but there doesn’t seem to be an option in Advanced Search to find these types of actions.
Trying the exact same thing, maybe try vote for this idea and maybe mendix grants us this feature somewhere in the future.