Question – Updating FBX files to include new animations

Hi!
I’m using FBX files for my project and I have a file containing multiple animations. Because the animations involve overlapping motion, I have to manually correct the start and end frames for each animation in the inspector. However, if I add new animations to that FBX in an external project, importing that new file requires that I manually re-edit all those overlapping animation starts and ends.

Is there an existing solution to “upgrading” or otherwise combining FBX file data in Unity? I’m sure there’s something I’m missing here.

Thank you so much!

– Porter