Hi T.L.M,
I downloaded your test project and attempted to reproduce what you’re encountering but I was able to save without any issue.
To be exact, after loading up the project, I made an actor blueprint and then added the ‘Create Flower Object’ blueprint node in the Constructor Script. After attaching the Constructor Script to the Create Flower Object pin, I dragged off the ‘Return Value’ pin of the Create Flower Object and selected ‘Promote to Variable’. After this, the blueprint looked like your picture does. I attempted to compile and then save without any issue.
I know your steps are pretty basic but are there any other details that may be omitted? It’s possible that I missed a step that you are taking that is causing the inability to save.