I've been missing the Altium "Find Similar" feature in my new Circuit Studio. But I may have found a work-around, at least in the footprint editor.
I need to change everything on the Mech12 layers of all my library footprints to MECH8 so that it maps to the Assembly Top layer on my new CS circuit boards. I was afraid I was going to have to select every segment in every footprint and manually change to Mech8 in order for this mapping to take place.
Please forgive me if this is old news, but I discovered you can easily change all selected items to another layer, by selecting the items in question (go to single layer mode and throw a window around everything you want to select) , then go to the Footprint Editor View/Object Inspector and select the new layer you want, hitting return and closing the window.
Now, if the View/Object Inspector in the PCB editor can somehow be employed to select all 12mil tracks and change them to 10mil tracks, or change all reference designators from 60mil tall to 50mil tall, etc. That would definitely be a bonus.