In edit mode, the middle mouse button should always pan, even when there is an item under the cursor
Currently, the "pan with middle mouse button" action seems to be implemented by treating a middle-click as a left-click. For example, if you hover over a text item and double-middle-click, the canvas will enter text edit mode.
This means that when attempting to pan the canvas using the middle mouse button, if there is an item under the mouse cursor, the item will be grabbed and repositioned instead. This can make it difficult to pan across busy scores.
I suggest that the middle mouse button should unconditionally start the "pan" operation (as though left-clicking in empty space), even when there is an item under the mouse cursor.