Nope, rebooting doesn't work
I also tried adding all my modelines to the EDID, but the behaviour is the same. I have noticed that when i install the modelines for the first time after re-imaging my drive, or to the EDID, i can see them listed in Win10 display settings. However, once i try to open a game, or even just change modes, they all disappear and i can only see the first mode in the EDID, and whatever mode i happen to be in. Or sometimes the display just reverts to the first mode in the EDID, and the resolution box under win10 display settings is showing that mode but is greyed out so i cannot change it. Restarting the system does not bring the modelines back, Windows will not see them anymore. Reinstalling them with VMM might bring them back (in the list, at least) but normally not.
Arcade OSD will only switch happily to the first mode in the EDID, which might be 320x240, or might be 640x480 if i haven't added my own modes to it. Trying to swtich to any other mode gives a sort of flashing black screen, like the system is trying to switch modes but cant. Sometimes this begins with a screen the right resolution, but the previous resolution set in the top left corner like a window. Then the screen goes black and sort of flashes or tics a few times, the mouse coming up and then disappearing maybe ten times, then the screen goes black. Hitting esc. brings the display back - sometimes in the mode i was trying to switch to, at first, but repeated attempts just revert to the first mode in the EDID.
(Test test mode watermark is happily in the lower right corner, and the driver says it installs no problems, in case you need to ask.)
I am about to go and flash a physical EDID dongle with the Arcade_15 preset (480i only). I will report back. But i'm happy to test or try anything else you can think of as well
EDIT: aaand the EDID dongle behaves exactly the same way as setting the EDID in VMM. Worse, in fact, because hot-plugging it is causing crashes sometimes.