Think I have corrupted this on my actual file that I'm working on.
Yes, I know that I can right click and get the panel back, but it's blank!
Have tried deleting export templates, tried opening on new machine!
You need to select an item on the composer page, for the properties to be shown for that item. Looks like you only have a map. Try to select it, with the select/move item tool in the print composer.
Okay, found it.
See that small box that says #Map0, clicked on it and Items Properties re-appeared!
In the Layout, you will see "view" on the top panel Click "view" and it will produce a drop down list, scroll down to "panel" Click it and a multiple option drop down list will appear. Now select "item properties"
