Can you have different frame rate timelines in 1 project?

I frequently need to work on clips in different frame rates - can you have timelines with different frame rates in the same project or are you forced to used the Project setting for all?

TIA

Seems everything needs to be the same framerate. That's an issue I'm currently dealing with since I'm trying to bring a timeline from one project into another but I accidentally set one to 23.97 instead of 24 and will refuse to copy over.