As a player, when dragging buttons in and out of the actionbar, the empty (or available) buttons should highlight similar to the standard action buttons

Example Usecase 1 : Dragging a spell, item, or macro

• Open Spell UI
• Drag Spell into the actionbar
• While dragging, the empty actionbars in ActionbarPlus should be highlighted in some way to make the user aware of the available drop targets

Example Usecase 2 : Dragging a spell, item or macro from ActionbarPlus action bars

• Drag a spell from an ActionbarPlus action slot (button)
• While dragging, the empty actionbars in ActionbarPlus should be highlighted in some way to make the user aware of the available drop targets

Example Usecase 2 : Dragging a spell, item or macro from WOW standard action bars

• Drag a spell from the standard wow action bar
• While dragging, the empty actionbars in ActionbarPlus should be highlighted in some way to make the user aware of the available drop targets