This issue is still unresolved in version 3.5.2 (MacOS).
After pressing OK (as "apply" is greyed out) all changes are lost.
As you can see, I've just selected Intelsat, but I can't save this due missing apply button.
I could now select/un-select e.g. "Draw satellites as stars" to let the apply button appear and save my settings.
Beside of this behavior I can only see Satellites in KStars when I de-select "Show only visible satellites".
macOS Ventura - 10micron GM1000HPS - ZWO ASI Camera - Baader Steeldrive II
Celestron 11" EdgeHD, TS-Optics Doublet SD-Apo 80 mm, Lunt 80THA/B1800FTPT