SureAI

I played + completed Enderal a while ago. I loved it, but I don't want to go through the main quest again. Instead I'd just like to play the Forgotten Stories quests, ideally with my old character. Is this possible?

Welcome to the forum

Unfortunately, old saves are not compatible with Enderal Forgotten Stories.
The new features (for example 2 new classes) have been integrated into the game and the first changes are noticeable early in the game.

Of course, once you're in Ark, you can start for example the two new faction quest lines, Golden Sickle and Rhalata. But for Rhalata, you should already have a higher level.
But these are not all new quests.

You can read more about this here in the wiki.