I’m using ACF Pro 5.8.7 and I need to use optgroups preferably with checkboxes.
I found this thread where someone wrote a core-hack to use optgroups with select fields. The last post claims that now (2014) this should work with an action hook, but the code snippet throws a fatal error.
Can someone please enlighten me where we are now, in 2019. Is it still necessary to deal with core-hacks to make this work in ACF Pro ?