Good day everyone,

Just wanted to ask if it's possible for krita to go windowless without using Full Screen Mode. Been checking the Configure Krita for such entry but seems nothing like this exist. Also checked the kritarc file to see if there are more options there.

If not possible inside Krita, do you guys know some way to do it outside Krita?

Choose windowed mode instead of tabbed mode in the settings. Unless you're using macOS, where the subwindow window titlebars cannot be hidden. This is not a bug in Krita; this is handled by a component lower in the stack.