Autoassign appointments based on category/ special field

is there any option to make use of the autoassign functionality (Appointment), based on an category/ special field?
Our agents have different focus and I would like to autoassign the appointment based on their knowledge (for “knowledge” I extend the user by eg three fields, “focus area 1”, “focus area 2”, “focus area 3”.

As per default there is no “special field” input available in the default app, I have to add a field for that first:

Any ideas on how to solve this?

Thanks in advance!