Add way to edit available items

[jrmi]

May a workflow like this:

• Create an element on the board, then allow to save it in box
• Element in box can be moved ? Group can be edited ? label is something like "catA>catB>Name
• Allow to delete elements from box

[jrmi]

First iteration could be to add a new button to the edit panel to be able to add an item to the available box then a button to remove it. No modification possible for now.

How to reorder it?