Seems like something with the FL interface has changed as to make the items in the bar not equippable. This is inconvenient for wanting to equip something useful. Not sure if this is something that can be fixed (or should be fixed if it was an intentional change by FBG), but here we are.
It would be convenient (for me) to have presets for events such as Festival of the Zee or Whitsun, as one might want to keep track of what items have been acquired already, or to post screenshots on social media. You might or might not feel the same.
As of a mid-week patch new equipment slots have been added to the game. Adornments, crew, and luggage can already be filled, while the airship slot is not visible in the UI for lack of a ship being acquirable yet (but whose slot is visible in the character profile). None of these are included in the custom section added by this addon at the time of writing.