https://bugs.kde.org/show_bug.cgi?id=479335. The above one will explain things I guess.
Unfortunately merging apps isn't really a thing. It's like saying that these two houses are each great in their own ways, and you should merge them into one house. The way you actually do this is to select one house, abandon the other, and improve the selected house in ways that add the elements of the other house while trying to avoid the ways that it wasn't ideal. It's the same with apps.