Oh. You’re using Kinoite. You didn’t even mention that, initially. Fedora KDE is not necessarily Fedora Kinoite, as you can run a KDE-based Fedora without using the ostree-based system core that Kinoite is built on.
Since you are using Kinoite, I’ll refer you to the Installation docs Known Limitations section:
Known limitations
Kinoite does not provide a fully functional experience for dual booting or manual partitioning.
It is possible to make Kinoite work for both dual boot and manual partitioning, and some guidance is provided on manual partitioning below. However, there are hazards involved in both cases, and you should only attempt to use these features if you have done the necessary research, and are confident that you can overcome any issues that you might encounter.
Dual-booting with Kinoite (a brand-new release type for Fedora that just debuted last week with the Fedora 35 release) sounds like it may not be the best option right now. You may have better luck with the Fedora KDE Plasma Desktop Spin.