So, here's the issue. When you have something selected and you manually enter the values in say the CMYK color fields, you would expect to be able to hit Tab to go to the next color field in the Color Panel. Instead, it exits the Color field and returns to the document, so that the next thing you type replaces the text you have selected.
In my mind its either a bug or a bad usability feature. In every other panel in Affinity Designer, the tab key goes to another field (example in the Guides Manager). In every other illustration and graphics program since forever (like Macromedia Freehand, etc.) the tab key moved the in panels moved to the next field in the panel itself and never exited the panel.
Thanks for fixing this bug.