Same here. I would like to import all my old Lightroom pictures into dt. I have already exported the keyword file from lightroom and imported it in dt: the hierarchy is conserved. However, when I import the photos (with the associated xmp), the tag database is suddenly populated with all the de-hierarchized (if that’s a word) 
tags.
Note that my tag tree is quite big and it is cumbersome to delete and reassign tags (by the way, I haven’t found a way to delete more than one tag at a time in the tag tree… is it possible?)
thanks for any help
giuseppe