Categories and Search Folders
Why don't you implement the categories and search folders that are available in the full client of Outlook? I know a lot of people who are using these features (as they are part of the Outlook Best Practices that are defined by Microsoft).
If you have categories already created you can add that to a calendar item by clicking on the 3 dots then clicking category then selecting the category. In most cases, I have had to create the item first then go back and edit the category.
If you have folders already created, you can access them by clicking on the folder icon and move items into them