The settings will occupy the window, if you open them in a tab by default.
That is also true if you're editing the Appearance settings or Themes. If someone is opening the Settings in a tab they clearly don't care about having live feedback to changes that they are making.
I hope that the developers are open to suggestions from users on making this a little easier to use. It will do, but it's not ideal yet, and probably would not take much effort to change. The existing problems with using a Panel for Reader View/Mode already need some fixes, which won't be needed if they are in settings:An entry in settings to assign a shortcut to the Reader View panel An entry to assign a mouse gesture. Renaming of the tooltip in the URL field from Reader View to Reader Mode, or renaming of the Panel icon tooltip to Reader View. Adding the Reader View/Mode panel to the Alt F7 shortcut to "Open Next Panel," and Alt Shift F7 shortcut to "Open Previous Panel." Currently, the Reader Mode panel is not included in panel cycling.