Hi,
By animation curves you mean raw data of joint transform animation?
Afaik, there is no built-in editor for these. But if you really need to edit it in editor and not able to use external tools and willing to spend some time creating a tool in BP… there is a painful way to accomplish this.
Using AnimModifier, you may get raw animation data (called Data Model and edited trough Controller (MVC programming pattern)). You may extract raw joint animation and bake it into curve data. Then it will be available to edit in Curve Editor. You’ll need to move edits back into Bone Tracks otherwise it may affect performance.
If you mean custom attribute curves, then i believe it’s already editable in Curve Editor when opening that animation sequence asset.
TL;DR
You probably better off using external tools. Blender is a great choice for such things.