I see that many ppl have a significant number of devices and and mine are growing steadily as well. This starts to make scrolling down the device list to look for a device a bit tedious. What I propose is to be able to organise devices into expandable groups that the user can organise (eg by room or function or however one chooses) .
I like the tagging idea. In the meantime, depending on how you named your stuff, you can search for "light" to see all the lights or a location like "kitchen" to see everything in the kitchen. That's almost like tagging and it filters in real time.
That way Kitchen Island Light and Kitchen Cabinet Lights show up in both searches, but Bedroom Light and Kitchen Motion Sensor only show up for the appropriate search. To take this even further, you can also search for "kitchen light" and it will also match both terms showing only Kitchen Island Light and Kitchen Cabinet Lights.
I only have 74 devices, but this makes it super fast to find what I need.
I've just started with HE and am still running Home Assistant in parallel. I have to say that I'm a bit surprised that something so basic like adding a device to a room, area, location is not available. In HA you have an Area view which lists all devices assigned to a particular room or area. I definitely want this feature in HE just for my sanity of maintaining hundreds of devices. Tagging might work if it can be filtered and searched on.
You might want to see this post by Lewis Heidrick (@lewis.heidrick) that shows one way to do what you want (organize Rules, automations, and devices) into groups: