This work to me but...
yeah, without inspecting-the-inspector I'm not sure what can be really done in it ๐
0_1520468670687_devtools.PNG
(It's just an unpacked extension which "paint" the rainbow on a .panel class)
On vivaldi://inspect/ devtool path is seen but then again.. don't inspect.
On remote(?) inspector http://localhost:9222/ which need a shortcut flag, dev tools can be inspected. But run really slow here (not sure why, maybe due chrome:// mods)