custom camera profile edit

User customised camera profiles (.dcp) won't save into the same location as the Adobe supplied ones (and even if you do force that, they would then not appear in the application). Rather, they need to be saved into the appropriate folder within the user files area - this is checked for new entries at each LR startup.

On Windows, that location is: "C:\Users\[username]\AppData\Roaming\Adobe\CameraRaw\CameraProfiles"

...noting that "AppData" is by default a hidden folder, so may seem to not be there.

What OS are you running? Mac? Windows? If it is Catalina you are likely running  into permissions issues and need to grant Lightroom Full  Disk Access via your System  Preferences>Security and Privacy.