When a customer rings asking for something one-off ("can you look at the patch by the gate?"), open the site's page and use Pin to next visit.
The note attaches to that site's next scheduled visit: the crew see it flagged on the visit and in their morning briefing, and the team is notified. You can also add it as a tickable task on that visit so it can't be forgotten. The pin dies with that visit — unlike a standing reminder, it won't nag every round.