Currently we can assign categories to an image (in the Browser) by displaying the properties panel, selecting the Categories tab, and checking off the categories the image belongs to.
What we cannot do... is add a new category there! Instead we have to display the Tree/Navigator panel, select its Category tab, create the new category, then either drag the image to it or return to the Properties panel (where we began) and assign the new category there.
This is too many steps!!!
Please consider including category management functionality (new, delete, re-order) in the Property panel's Category tab.
Full Category Control in Properties Category Tab
Moderators: helmut, XnTriq, xnview