A dialog for File->Merge

[micheus]

Thank you guys for get into this discussion.

Yeah, we can have an option related to selection. I thought in something like this:
┌─ Selection options ───┐
│ ● Preserve selection ∙│
│ ○ Add to current ∙∙∙∙∙│
│ ○ Replace current ∙∙∙∙│
└───────────────────────┘
But, I'm not good with name, so I'm accepting suggestions.

The Selection groups are being preserved too, but is it interesting preserve it in case it become invalid? (case in which elements that are part of the selection group belong to a not imported object)
The same case can be applied to Folders.
What do you guys think about them?