If you’re using GUI v1 then you can install @kwindrem his GUI mod, then you have a dedicated relays page, and you can also rename them.
If you’re using GUI v2 then you have to wait for a dedicated relays page to be implemented. In the GUI v2 Beta version topic, Victron @mpvader wrote that this request is on the radar.
I hope this option will be implemented soon, and till then I stick to GUI v1 with the GUI mod.
Here’s the same request: Eigener Name für Relais, Dig Inputs und so - #2 by Theo