The Category field in the Event editor dialog of version 2.11 seems to have lost some functionality compared to a previous version of Rainlendar (2.9, I think).
In 2.9, when you enter the category field and start typing a few letters, it automatically fills in the matching category, along with colour and icon. Pressing Enter would close the dialog and accept the changes.
Now in 2.11, it does not autocomplete the category, or show the icon, and hitting Enter while the cursor is in the field does nothing. It also doesn't work properly in the tab order. If you activate the field using the mouse, hitting Tab takes you to the previously active field, not the next in the chain.
Windows 7 x64