Reusing animations for an iso character is possible, but you have to set up the skeleton to accommodate this animation from the beginning. So there may or may not be a way for you to reuse the animations you've created. Could you post some screenshots, GIFs, or YouTube videos of what you have so far?

If you have an isometric character, you should have an animation seen from the front and from the back, and then just mirror it at runtime or in Spine by scaling a parent bone that acts as container of your character to -1 on one of the axis.

If your character is isometric you'll likely have started with the South-East or South-West animation, the next logical step is to rearrange the assets and the draw order so that your character is facing the opposite way in an animation. You'll likely be able to reuse many parts of an animation such as the body movement but you'll need to redo things like the feet in a walk, for which you can first do one foot to mimick the other direction in reverse. Having visual guides as background images can help speed this process up. Don't forget constraints properties such as the direction in which an IK bends can be keyed in animations as well!

There's a serie of streams about creating an isometric character (walking in 8 directions because we like complicated things) here:
Spine: Twitch: video SS5JGbD5BJY
You'll also find a downloadable project alongside the complete rigging process, plus chapters to jump to what interests you the most.
I suggest to try to give this a go, and if you have further questions, I'm here to answer