Thanks, that’s fixed it.
The syntax is quite specific, for example, you need to put “yes” with a lower-case y, not “Yes”.
In the Custom Field Name box you need to enter: “synved_social_exclude_share”
In the Custom Field Value box you enter: “yes”
To get Custom Fields to show-up in the first place, at the top-right of your Page/Post screen, select ‘Screen Options’ and under ‘Show on Screen’ tick the ‘Custom Fields’ box.
Synved, thanks for your help.
Mods, Please mark this topic as resolved.