You can merge (combine) two or more events in a library (for example, if the media and projects they contain are very closely related). If you find an event is getting bulky and unmanageable, you can split it into multiple events.
In the Libraries sidebar in Final Cut Pro, do one of the following:
Drag one or more events to an event you want to combine them with.
Select the events you want to combine, then choose File > Merge Events.
The events are merged into a single event in the library. The corresponding source media files remain in their original locations, either in the library file or linked from external folders.