Hello, I am on an updated EndeavorOS/Arch. My Dolphin says it's on 22.12.0, frameworks version Version 5.101.0. Latest polkit and polkit-kde-agent and kio are installed.
I see many sources say that polkit support was added to dolphin a year ago, allowing it to perform root actions without being run as root.

I do not see any thing related to Dolphin in /usr/share/polkit-1/actions/

My dolphin cannot do any modifications to any files that require admin permission to edit; dragging files results in an access denied error, and Create New, Cut, etc. are greyed out. Other KDE applications that use polkit seem to work fine.

How can I fix this issue?

I don't use endeavour but going from what I did in Ubuntu.. Look for a package to install called kio-admin. If you can install that you can right click in a dolphin directory you can't edit and there is an "Open as administrator" option.

Not sure this is implemented yet. So yeah, kio-admin or use the " open as root" service menu.https://store.kde.org/p/1384645/
Btw. You can't edit root files as non root. What the aim is, is to be able to do root stuff in dolphin which you'd do in a non-root window by popping up a polkit kdialog. You can do that now by editing a root file with kate. That's how it would work. Say, for example, you want to drag a picture to a root destination, it'd pop up the same kdialog.https://imgur.com/a/adKMcfA