When in edit mode the X appears over the procedure but clicking it does not remove the pinned procedure/page. Going into the menu navigation for the airport and manually clicking the pin to remove it, also does not remove it.
When this is enabled, it isn’t possible to remove the charts which it is keeping in sync (typically Airport diagrams, SID, STAR and Approach). You can remove the charts you pin yourself.
To completely edit the pinboard, turn off the Sync option.