1. Ad Single field
2. Field Type Custome field
3. Post Source Current post
4. Custome field Groups "xxxxx"
5. Field Settings -Output mode -As described in the following format
here is the problem format option is missing for me.
How can you activate it?
Is there any documentation that you are following?
hidden link
Is there a similar example that we can see?
What is the link to your site? hidden link
I work in a staging mode you cannot see