Well, as you can see in the image posted above the CPU/memory sliders are also not greyed out for me, so that those does not work in your environment does not really add much new info.
Something is clearly not right in your environment (but working elsewhere, e.g. for me). Whatever the settings application is looking for to “un-greyout” does not happen on your machine. Have you tried a factory reset?
If factory reset or a complete un/reinstall doesn’t clean up your environment I guess you can open an issue on GitHub providing as much info about your environment as possible via Diagnose & Feedback posting the diagnostic ID OS version etc.
I just did a factory reset. The Advanced Settings still works after that. Here a few detailed observations I hope will be useful to someone who need to troubleshoot their environment:
Factory reset also resets
%APPDATA%\Docker\settings.json including the VHD location which now is
null so it points to the original location. To learn a bit about how reset works before doing the reset I had set an alternative location for the VHD. The factory reset apparently removes a possible
MobyLinuxVM VHD in the factory location (observed in Hyper-V) but leaves a possible alternative VHD alone. If the reset is performed while in Windows container mode it is on switching to Linux container mode the re-download of the VHD is triggered.