Hi:
Thanks. I actually want to add a class around a group of fields already inside the metabox. Adding the class on the metabox affects all fields. I want to add the class only around one or more groups of fields inside the metabox.
The only solution I was able to arrive at for this was to directly modify the metabox-columns plugin.
I modified it to accept two more values in the metabox array of fields "column_row_before" and "column_row_after" which allows for injection of the field class before and after any field 'row' without automatically closing up starting div.
I was hoping to be able to submit that as a PR against your repo but it's not a public repo.
There's probably a smarter way to do it - maybe by wrapping things the way the metabox group module works. But didn't want to spend that much time figuring that out.
Here's an image of the code changes for anyone interested.
Thanks.