Modify Specific Frame FBX Animation

Hello Everyone,
I have a problem with my FBX animation purchaed on the Unreal Store ( Animation pack)
I try to modify the mouvement .

but the modification have effect on all the animation.

I would like to know if we can modify an animation only at one specific moment .
For example in Iclone you can adjust a mouvemnt to match your environement

Is this possible in Unreal 5.X ?

Thanks in advance

Solve with the additive layer track