Two things here.
One way to handle a bunch of devices you don’t want to look at (often) is to create a room with a name that sorts high alphabetically, so it ends up at the end of the list of rooms, and then put those devices in it. For example, I have a group called “Virtual Devices” where I put the Reactor master device, my Rachio sprinkler plugin, my SiteSensor instances for weather and Internet health checks, etc.
The other thing is that if you have a large number of ReactorSensors, you probably are not taking advantage of condition groups and group activities. Using condition groups lets you combine the logic of several ReactorSensors into one, thus requiring fewer ReactorSensors. I group mine by room by default: one ReactorSensor per room that handles all the work for that room. I have additional ReactorSensors in my Virtual Devices “room” for generic functions used by many or all of the rooms (the room RS’s can use a “group state” condition to check the day/night RS in the Virtual Sensors room). In one case, my home theater, I have one additional RS just to manage the AV system, in partnership with the room RS to manage lighting and other things.