Thank you so much for this detailed answer! It’s really helpful!
I have one follow up question though – concerning the “construct layout” step and I would be really grateful if you could explain it a bit further. Does it mean that I build the content of $flex_field within the post first, and then dump the $flex_field? I suppose that gives me a nested array with all the layouts in order?
Thanks again!
If someone else finds this topic and wonder why it’s not working – you have to edit the “modified” value of the field group. Otherwise, it won’t recognize the change and the “sync available” option won’t show up.