I used skinparam tabSize 2 and used tabs for structuring multiline messages, but it seems to be broken in the latest version.
Here's a reproduction: https://www.plantuml.com/plantuml/uml/SoWkIImgAStDuIhEpimhI2nAp5KeIKmApgnALJ3YudBAJrBGjLDmpCbCJhLIK4gCoOifILBYSaZDIm7g0G00
I tried to find info that maybe this was migrated to the new CSS styling, but couldn't find any docs for that. Is it still supported somehow?