[Disinto]

 When you activate HDR or deactivate it do you see your picture change quality hugely (i.e. does it switch between an HDR10/PQ EOTF and an SDR/BT.1886 EOTF?)

(EOTF is just the accurate way of describing the way a video signal is converted to light output from your TV. SDR and HDR video has different EOTFs)In addition, there's no segregation for SDR and HDR picture adjustment. The closest option I could find was custom settings, i.e. I could leave the standard image profile settings for SDR streams and use a custom profile for HDR10 streams, but that obviously would require a long and tedious calibration, since the TV doesn't seem to be able to recognize the right EOTF.
You are conflating having separate calibration for SDR and HDR with there being separate menu options. On many TVs - Sony for instance - when you are in HDR mode (i.e. watching an HDR signal) your picture adjustments are made and stored ONLY for HDR content, and don't alter the picture settings for SDR. When you alter the same controls when watching SDR content, they are only adjusting those picture settings for SDR content (and don't change the settings for HDR content)

It's just the same way that picture settings are separate for each HDMI input, for the Digital TV source, for Online TV apps etc. - settings made whilst watching the DVB tuner don't apply to those used when watching the HDMI 1 input for instance.

This isn't true of ALL controls - but it is true of most of them.

Do you have the beta firmware that added HDMI Colour space switching and enabled the Developer option that then lets you enable HDMI Colour space switching ?

If you don't I'd chose Rec 2020 colour space and 12 bit 4:2:2 output as a default (if your TV supports it) 

Hi there,
The only HDR option on my TV is "on" or "off" I then configured the SHIELD to in YUV 4:2:2 12-bit Rec. 2020, which is the maximum supported by my TV.
I don't see any visible difference on my TV when activating this mode, no visible color shift.
I have the latest official firmware/SW upgrade and it already comes with the the option to activate the HDMI Color space switch in the developer mode. I activated it, but it didn't yield to any visible change when playing an HDR10 movie.
I tried 2 movies to make sure (I checked their characteristics with MediaInfo), but again, no change.
Lastly, alas, it seems that the picture controls on my TV are common between SDR and HDR. I tried to play a normal movie and an HDR10 one, with different resolutions, and any change in the menu in one mode was carried over in the other mode.

Finally - initially my TV didn't come with HDR activated but I think it was delivered in a subsequent firmware update.
I can't exclude the fact that HDR mode is buggy on my TV, it's fairly old (LG UF680T)