Today I downloaded Mcreator 1.8.1, so I exported the workspace of Mcreator 1.8.0 into MCreator 1.8.1.
The first time I imported the workspace it said it was older than 1.7.9 (and that was a 1.8.0 workspace) and I pressed ok. It imported the workspace in very little time but it actually imported nothing. It didn't import any mod elements/textures/etc.
So I tried to import it again and I had the same issue.
I thought that MCreator 1.8.0 generated an empty mcr file, so I tried to export the workspace again (with a different name).
I closed and opened again MCreator 1.8.1, then imported the new workspace.
It didn't say that the workspace was older than 1.7.9 and it imported all the elements.
I thought it was working fine, until I pressed runclient and had this error: