When I drag a folder to a toolbar I always use the argument
NEWTAB=findexisting and occasionally
OPENINRIGHT/LEFT which I have to add manually afterwards. Is it currently possible to add these arguments automatically by holding down a qualifier key when I am dragging them, and if not would it be possible to add such a feature?
If each different type folder button is grouped together (not mixed or spread around) then you could use Favorites to make things a bit easier. Make a branch of Favorites for each type of shortcut, and a button which lists just that branch plus the extra arguments, and then add folders to the favorites branch you want instead of making standalone buttons for each folder. Then you can pick the branch to add them to each time, by selecting from a list.
Unfortunately the folder are spread out all over the place so this method wouldn't work. Good for know for other cases though