I'm running PM 6.0, build 6890, Win 11 Home 22H2.
I noticed recently that my locations list has developed a weird nesting issue. I suspect this came about shortly after I added a new location with a name enclosed in quotes, knowing what unanticipated quotation marks can sometimes do to strings. I edited the location to remove the quotation marks, but the issue remains.
The attached screen shot shows what is happening. The locations list shows two "top level" entries, that are actually multiple individual entries. Under each is a sub-menu of my locations, divided into two groups. The complete list shows normally in the edit window. I've exported my locations list and attached if that helps.