Make sure to read what KaOS is and what it is not, it certainly is not Arch based, or compatible with it:
Especially read the part about filesystem setup. You just need to force install one package to irreversible break your KaOS install, and posting about doing that will be automatically deleted in this forum. If you want to break your install, no-one can stop you, falsely inviting others to do so too, will not be tolerated.
Using KCP, or package building is certainly not hard, and well documented, so you can add whatever you want to your install that way, without breaking any. Though krename is in the repo, not clear why you think you need a GTK app instead.
The limited repos also means, there will be a limited number of filemanager offered, Dolphin is extremely powerful, few other, Qt/KDE based are offered. GTK apps will always be limited here, and only offered if no real Qt/KDE alternative is offered.
Closing this six!! year old thread, please don't necrobump like this, you did receive a warning while posting not to do so.