Event Categories are used in the new events system, mainly to separate them into more digestible chunks.
After creating an event category, you can open it by clicking the arrow button on the entry in the category list.
Category settings apply to all events belonging to this category, regardless of the event's individual settings. Updating these won't overwrite any settings on the events.
Hide from viewers
This will hide any events this category is assigned to, regardless of its own hiding settings.
Usable by players
If you are subscribed to the timekeeper tier, your players can add events to your calendar, and by ticking this you will allow the users to select this category when creating events.
Any changes to the settings under this title will overwrite the settings of all events assigned to this category.
You can still go back into the event and individually override settings, but be aware when you change the settings below.
Fully hide event
Similar to the event's own fully hide setting, this will hide the event not only from your players, but from you as well. This might be useful if you have events with conditions based on other events, and want to limit how many of them are shown.
This will hide any events under this category from anyone viewing your calendar.
Show when printing
If you go to the print view, this will make any events under this category show up.
Color and Display
This changes how any events under this category is displayed. The various color and display combinations will allow you to easily differentiate between them.
This setting determines what event category is automatically used when a new event is created.