Let’s say I select 4 items to Fade In, but later I determine I want 5 items to fade in at that time. Is there a way to edit that specific Animation to simply include the last/5th item? Right now I’d probably select the 5 items and create a different Fade In Animation, and then swap it out for the old, but just curious if that was the best practice or not?
The method you explained is the best practice. If you want to include an additional object in an animation you can just select the objects, add the animation and remove the former one.