Add pop up copied paste on variant

[C-Vlad]

Hello,
As the design options are getting more and more usefull, we stumble upon the same problems as layers, but more critical in this context: lack of 'special paste'.

When we copy an element, and paste it on another file, if it comes from a design option, and the option does not exists, it creates one, and it is disabled by default. This is cumbersome to work with multiple files.

The wish here is: Add a 'special paste' function, that allows to select the design option, and the layer the element will be placed on.

[scottjm]

I think this ties into the way in which attributes are imported when copy/pasting element.  Hopefully this can be added to the roadmap of that area of development.