As discussed on IRC. If a user is in tabbed mode and wants to duplicate a particular group of layer or several layers into any other open document he needs to switch to sub-window mode and then drag the layer or groups to desired destination. This becomes tedious so i suggest making the tab activated while dragging from one document to other, so the user needs to drag the layer or group to desired tab. Alternatively ( this is how photoshop does it) we can have some kind of menu item added to the right click menu in layer panel. Something like duplicate group or layer and then the user gets to choose the name of open document where he needs the group or layer duplicated. i hope i am clear enough in explaining the feature. Reproducible: Always
Dmitry has added drag and drop support for tabbed mode in this commit https://quickgit.kde.org/?p=krita.git&a=commit&h=b7170a05e3697419a3cd14ed905fe8428a1a94dd As far as the dialog box is concerned boud told that it can be later done with scripting. I am closing this bug :)