Elite Dangerous, specifically, seems to re-acquire the SteamVR recommended render resolution every time one change one of the game's own ss/hmdq settings; So as an alternative to relaunching the game, one can hop into settings, change HMD Quality to something else, and then back to 1.0 again, to make one's new SteamVR render resolution setting "take".
It is, of course, also possible to
make Elite gobble up all one's VRAM - it really looks quite nice, and "tangible", with a ton of supersampling, 16k skybox (especially if one alter one's galaxy map parameters to make things a bit more eventful), and 8k planet textures - of course the frame rate when doing 400% render target on a 20+ ppd VR headset becomes rather slideshow-y. :7
I find a 6k skybox makes a, to me, tolerable balance between looks, and hyperspace jump time (during which the skybox is rendered), as long as I'm not going to do too many consecutive jumps; And 3k planets for rendering to a Pimax8KX, at x1.5 quality (225%); Any less, and the night lights on an inhabited earthlike looks "blobby"; More, and they begin to exhibit quite a bit of aliasing (...which can be balanced with more supersampling

).
( Don't know if this has changed, but an upper limit that SteamVR has to the bitmap size it recommends to a game, at least
used to default to 4096, and any SteamVR render resolution past that would be reduced to fit inside that frame, even though a larger number would be shown under the supersampling slider. This can be increased (to e.g. 8192), with the key: "maxRecommendedResolution", in the "steamvr: {}" object of one's steamvr.vrsettings file. )