JOSM: Copy tags from relation to line

Someone has created a building as multipolygon. Unnecessarily, it has two outer lines forming a simple rectangle.
I want to change it into simple rectangle. Is there a way to copy tags from relation and paste them to the line?
I know the paste tags feature, but I don’t know how to get relation into clipboard…

I stumbled on this the other day. . . I’m on a Mac and the key combos might be a bit different for other operating systems.

Right click on the relation in the list and select “edit relation”. All the key/values show up in the place where you normally edit ways and points. Right click on that and select “copy all tags/values”. Now select the way you want to put the tags on and do the shift paste. You will have a type=multipolygon tag that you should remove after the paste.

OK, I had to do some trial and error on PC, but there it is:
There is no “Edit” when rightclicking on relation. There is an “Edit” button, but it opens separate window and I could not copy tags from that.
But, there is the “Add relation to selection” option on rightclick (the name may be different, I have translated from Polish) and then all tags are in tag window and they may be copied from there.

Thanks :smiley: