GitHub added Reusable Workflows in 2022.
I looked into this in the summer of 2022 and found it didn't really reduce the size / effort for maintaining an action or a workflow, it seemed to just add to the complexity for releasing as it was one more moving part that had to be updated in a somewhat lock-step. Based on requirements for using pinned SHAs, it seemed like it would require one to create an additional commit just for the reusable workflow part which gave me a 🤯.
That said. It sounds appealing and there's definitely interest.
I'm hoping to work w/ a couple of people who are trying to make it work and we'll see if we can put something together before summer 2023 (hopefully sooner, but...).