SUMMARY
In the Specific Color Selector, colors beyond values of 1.00 can't be accessed unless the exposure is set sufficiently low.

Any color space, RGB, 16 or 32bit float color depth

STEPS TO REPRODUCE
1. Open new file with 16bit float and RGB color space
2. Set up Lut-Docker to use OpenIO and Color Module OCIO
3. In Specific Color Selector Docker, type a value greater than 1 in any field
4. lower exposure in the docker (or via Y+dragging up/down)
5. type value greater than 1 again

OBSERVED RESULT

Color clamps to what ever, depending on exposure level, would currently be displayed as maximum brightness color, regardless of chosen OCIO profile as input or view.

EXPECTED RESULT

When typing it in, color is unclamped in color depths and color spaces that work for HDR workflows, even if the resulting color might be too bright to display at the moment. Perhaps just give an over exposure warning inside the picker.

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Krita

 Version: 4.2.2
 Languages: de, en_US
 Hidpi: true

Qt

  Version (compiled): 5.12.4
  Version (loaded): 5.12.4

OS Information

  Build ABI: x86_64-little_endian-llp64
  Build CPU: x86_64
  CPU: x86_64
  Kernel Type: winnt
  Kernel Version: 10.0.17763
  Pretty Productname: Windows 10 (10.0)
  Product Type: windows
  Product Version: 10

ADDITIONAL INFORMATION

The permissible ranges of the sliders also change as you change the exposure. At an exposure of -10, the sliders go all the way to 1024. That is probably fine.