There’s not a trick for it. If you have a custom ACF field, say it’s key is named some_field if your condition checks for the presence of a value i.e. is not empty then it will return true. is_empty is_not_empty checks for the presence of a string value (or not) depending on your conditional.
I should have been clearer. I want to create my own version of ‘is empty’ in a custom condition. But I don’t know how to get rid of the extra field.
Many of the comparisons have 3 fields: field, comparison, value. ‘Is empty’ doesn’t have a value because it doesn’t need it. How do I do that in my custom comparisons?