So suppose I have three animation sequences, and I want to use one of them to only animate the left arm, the second to animate the right arm, and the third to animate the rest of the body. What tools should I use to do that?
Have you looked into animation montages? They can combine and overlap animations for your character. In fact, here is an Unreal Engine official tutorial that animates the arms separately from the body using montages:
I hope the solution above works for you!
Thanks for helping, but is there a method with blend and animation nodes, instead of montages?
There is a way to use blend/animation nodes! I suggest using layered animation! However, layered animations still use montages because they let you dynamically apply animations directly to specific bones and all of their children. Here is the documentation on Layered Animation:
Hopefully this is more directly what you are looking for.