Airtable automations can do this quite easily, the buildout of the automation varies depending on the naming conventions for your events.
If you only need a single category tag for each event, and most events have something in the event name that alludes to a category, it might look like this:
Create a 'Category' single select field with a list of the categorical options you use, add "Unidentified" as an option (this is done in the events table).
Create an Automation with the following configurations:
Trigger: When a record matches conditions...
Event Name is not empty AND Category is empty.
Then use conditional groups along with the Update Record action to execute the tagging.
The condition for each group will look like "Event Name contains XYZ (ie. Tour)"
For each group, use the Update Record action to add the corresponding tag to the record (ie. Category: Tour).
The last condition (the Otherwise action) should tag the record as "Unidentified." You can then manually update the Unidentified records, assuming that there's only a few of them.