I purchased a Razer Blackwidow V4 Low-profile a couple of days ago. I see as of SignalRGB 2.5.26 - 12/18/25, this keyboard is supported in both the wired and wireless modes. All the keys light up except the backslash \ key. I’ve tried to manually set the key to a color through “Devices > Razer Blackwidow V4 Low-profile > Lighting > Paint” but it doesn’t light up. I’m using V2.5.29-beta+4f56083d as of this post.
It’s most likely an issue with the layout I would imagine. Could be a variant of the keeb perhaps. I’d report the bug using the bug icon in the app (upper-right corner) or through this link so that the support team can follow up.
Thanks for the reply. I reported the issue using the bug icon.
And just for clarification, the backslash key \ does light when using Synapse 4’s Chroma mode or using the built-in color patterns (using fn + ctrl + #). It just doesn’t work when SignalRGB is running.
That means the hardware is working, and definitely means it’s something about the plugin for that device. The support and dev team should be able to get more insight while looking at the logs. 
It been 2 weeks since I submitted the report but haven’t heard back. So I went looking and found the problem. In “Razer_Modern_Keyboard.js”, lines 577 and 616, value for the \ key was “0” and should be “79”. I backed up the .js file, changed the values, and restarted SignalRGB. It worked. The \ key now lights.
Can someone at SignalRGB please make note of this fix, verify it, and update the Razer_Modern_Keyboard.js file?
That sounds correct, the plugin needs to be adjusted. DM me your email or ticket # and I can look into why you didn’t get a response, and also add notes regarding what solved things for you
Thanks for the reply. I sent a DM. I’m just happy the \ key is lighting. Hopefully this helps others too.