Blendspace and Anim Composite

I’m trying to remake one of my older games in UE4, so I’m trying to use the same assets as I used before. I used a really old animation tool, can’t really convert into new ones, so either I use completely the old assets, or have to reanimate everything.

My character model is in one file, with animation. The animation is not separated in actions, I just have a 1-500 framed animation, so I need to cut the animations into seperate actions.
I used AnimationComposite for that, because in the descriptions, it says it can combine animations, and handle as a normal AnimationSequence, and it works fine.
My problem is, that I’m trying to create a blendspace for movement( idle - run forward;back;left;right ), but it just does not accept AnimComposites.

Am I doing something wrong? Is there any way I could achieve it without modifying the content?
Thank you