Can I keep notes about my regular customers in the system so my staff know their preferences next time they book?

Yes, you can. Travel agency software normally keeps a customer record for everyone you have booked for, and alongside the basic details you can add free text notes such as a preferred airline, a window seat, a floor they like, a dietary need or a reminder that the traveller is nervous about early departures. The next time any member of your team opens that customer, the notes are there on screen, so the person answering the phone does not have to know the customer personally to sound like they do.

In most setups the record also holds the traveller's past bookings, so your staff can see where they have stayed before and repeat something similar without asking again. You can usually search customers by name, and some portals let you tag them, for example as a corporate traveller or a repeat honeymoon client, so you can pull a list later when you want to send an offer.

There are two honest limits. A note you save for your own team is not sent to the airline or the hotel automatically, so a preference still has to be entered as a special request on each booking, and the supplier decides whether to honour it. How much of this you get, and whether you can tag and filter customers or only type plain notes, depends on your plan and on the portal you are using, so it is worth confirming rather than assuming. You are also responsible for keeping personal details safe and only holding what you genuinely need.

Have a look at a customer record in your own system, add a test note, and check who on your team can see and edit it before you ask your staff to start using it properly.