@GrasDK well done on an initial post. I see you have new post since I started this. I will respond to it in another post, but these are some refernces to look at.
Just a comment about your new post: You have 3 switches that you will need to reconfigure, and they all use a different configuration “language”. If this is your first time, you are overly optimistic to think that 10 minutes will be enough time. It doesn’t help that the RB5009 is your main internet router, and that you can’t test things in a lab environment. Working around family members is in many ways harder than in a work environment, where you can often schedule things for off hours.
Having a good plan will minimize the chance of screwing things up. And make backups of everything before you start making changes, and have a good fall back plan.
What were you using as a router before the RB5009? Is it still available? Just in case you need to access the internet if things don’t go as planed.
Several questions.
You state you are moving from single lan to multiple lans. Is this your first experience with vlans? If not what type of equipment have you configured vlans on before?
Where is your UniFi controller? Which vlan? Have you asked any questions on the UI forum?
Have you already adopted the UniFi APs into the controller? Are you using the default of untagged “management” access to the UAPs? That can be changed to a tagged vlan, but unless you are a purist that want only tagged vlans on a trunk link, all the equipment you have should allow you to have a “native” vlan that is untagged going to the UAP. MikroTik terminology for a trunk port that has traffic using an untagged vlan is a “Hybrid” port.
Here’s another thread worth reading: RouterOS bridge mysteries explained, but it presumes you understand vlans and how to configure an external switch. It is essentially trying to explain how to wrap your head around the MikroTik bridge “combination” device. These are two comments I made about the post that explained some thing I learned when playing with my hEX S post 18 and post 19
And the Mikrotik documentation is worth reading as well. The RB260 configuration is quite different (SwOS) than the RB5009 (ROS) or the UniFi switch. When you get done you will know much more about vlans and configuring them than you did when you started. Here’s the ROS help Bridging and Switching and this section Bridge VLAN Table For the RB260 see this SwOS/RB250-RB260-VLAN-Example