Under “Connection” the “Port” field contents are shown in grey when “Display Number” is set to “Auto” suggesting that the value cannot be altered - which in that case it should be so - yet it can be altered. I appreciate the “Display Number” is changed accordingly when the value is altered but it’s shabby.
The option “Keep existing viewer if a new viewer tries to connect” under “Sharing” is a dependant of “Allow only one VNC connection at a time”. This relationship breaks down when one selects the controlling parameter and sets the dependant followed by selection of a different controlling one - i.e. the dependant stays set.
The “Port” field contents are shown in grey when “Display Number” is set to “Auto” suggesting that the value cannot be altered.
The initial value showing in grey is called a placeholder value and just shows you that it’s a default value that hasn’t been explicitly assigned. If the field were disabled the label would go grey.
For “Keep existing viewer if a new viewer tries to connect”:
This is valid for both “Let Viewers Request…” and “Allow only one…” and the checkbox choice will be honored. If “Allways allow multiple…” is selected then the checkbox selection is meaningless (and the interface item disables). We do retain your checkbox preference in case you return to one of the other modes.