Configure -> Satellites -> List of Satellites
Select one or more from the list -> the "Apply" Button stays grayed out.
You can only press "OK" or "Update TLEs"

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".

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