Save the trades you already use, and understand what happens when you have nobody for a job.
Your contractors are the trades you already use. Save one, and it is offered first whenever a tenant reports something in that trade — so nobody goes looking each time.
On a property or building's Maintenance tab, select + Add contractor, then Someone new.

Give their name, their trade, and at least one way to reach them — email, WhatsApp or phone. You drag those into the order Alfred should try.
There is one record of each contractor: adding them to a property or building assigns them, it does not copy them, so an edit anywhere updates them everywhere.
If no contractor is saved for the trade, Alfred searches near the property — Checkatrade and Google — and brings the candidates to your Inbox to approve. He never picks one for you.
Approving a candidate uses them for this job; save them under contractors if you want them offered first next time.