Okay nevermind, it works with “Label” if I change the url to “?converted_classes=[label]” instead of using the value in the url.
However, it’s only working for the first selection. For example, if a post has both the classes “Class_A” and “Class_B”, then only “?converted_classes=class_a” works.
EDIT: I just noticed, looking down at the default WP custom fields section on the page after I save/update, that it’s only adding a meta value for the first one. So if I select “Class_A” and “Class_B”, it’s not even adding the meta value for “Class_B”.
