This item references this ticket...https://phabricator.kde.org/T7782
This moves a lot of stuff that was in the splash screen startup page to the blank MDI area. This also removes the "Hide on Startup" for the splash page as well as the options that are in the MDI area now. The About area still has the links.
I did add thumbnails to the recent documents. It limits the amount to 5 recenty documents.
If you hover an image over the blank area, the blank area will now have a dotted rectangle indicating the whole area is droppable.
All this code is in the petrovic/welcome-screen branch if you want to see more bite size chunks of what the changes are actually doing.
I disabled the toolbox buttons so you cannot click them any longer if no documents are open.