I am a newbie to the CC system and I have tried to find the Extension Manager for this set of applications (in the Photographer set), to no avail. Have searched everywhere and do not find anything by that name as suggested in your page at https://helpx.adobe.com/extension-manager/using/extensions.html.
I can find some Adobe Extensions in the System/User Library tho.
Is the name as given here the wrong name (Extension Manager), could it be the Creative Cloud drop-downs from the Mac menu bar at the very top of the Mac's screen?
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