DnD to MTP Android volumes
Similar to #866 . Drag-and-drop to Android MTP volumes in the sidebar is currently not possible, since the only way is to manually open these in a new tab first, then open the "Internal Memory" (or SD card) row, and finally drag the file there in this way.
A solution for the simplest case would be having some sort of "transitive" DnD, that is, if the volume is a MTP one and presents only one child for "internal memory" or SD, drop the file there automatically.
A more elaborated solution would involve a dialog (design needed) or a popover attached to the MTP volume to choose if to drop the chosen files, for example, to flash storage, SD card 1 or SD card 2.