I tried dragging a material from project to project - did not work
Tried exporting - it exported it as .COPY , which the other project did not recognize
Tried to “Migrate” - did not have the other project open.
I misread the “Migrate” dialog title, it said that the following assets will be moved. I thought it asked me where I want this to be migrated. I had to click OK and navigate to the other project’s content folder.