How to refund planetary item or ship items upgrades?

I see the text saying "refund item for xxxx" but I have no idea how to refund! It's as clear as mud how to refund your ship items. I've tried left clicking, right clicking, ctrl left click, ctrl right click, shift left click, shift right click, alt left and right click, nothing works. How do you sell ship/planet upgrades to swap them out?

 

EDIT: I think I figured it out; you have to drag the item out away from the slot to remove it. Leaving this here in case somebody else runs into the same issue.