I would like to create a repeatable field group that is conditional, i.e. is displayed in backend and frontend input form(or not) depending on a selected option in another field, however I don't find a conditional option in repeatable field groups. Is this not available?
There is very limited support for this, I'm afraid, because of how Repeatable Field Groups (RFGs) are implemented, using child post types to store each instance of a group of related fields.
In the backend it sort-of works, inasmuch as when editing a post you have both the normal custom fields and repeatable field groups included on the same form.
You can add display conditions to the fields within a RFG individually, depending on the value of another field, and this works. But you can't conditionally display the entire RFG, only the individual fields within the RFG, so you still see the title of each RFG instance, for example, even if you cannot see any of the fields within the group.
On the front-end the workflow for adding instances of RFGs to a post involves a separate form to add one instance of a RFG, so the form for the post itself will include normal custom fields, but it doesn't contain the fields of the RFGs, which are in a separate form. Because the forms are separate, you cannot make the visibility of the fields of the RFG dependent on the standard fields.
In front-end forms, the workflow to add RFGs is a little cumbersome, you first publish the post with standard fields using a conventional form, and this would redirect to display the published post. The template for that post would include a link to a form to add RFGs to the post. You could conditionally display that link according to the value of some field previously submitted, only showing the link when the condition was matched.
Thank you very much for your extensive reply, that is very helpful.
We understand now it is not possible to add a conditional repeatable group as a custom field.
The front-end solution you mention, with a two-step approach, first adding data to the normal custom fields and then to the fields in the repeatable group on the published post page, would not really work for us.
Is the child post type the only way Toolset could integrate and implement the repeatable group? For frontend users this will be very confusing. They expect to enter all data in one form. I have no idea yet how to solve this obstacle.
Unfortunately that's how repeatable field groups are implemented, and there is no alternative.
The original intention was to update Forms so that you could publish/edit a post and its repeatable field groups all from the same form (just like you do when editing a post in the backend), but that work was never completed.
I wish I could say that forms will be updated for this soon, but I know it is just one of the many demands on the developers, though the more people request it the sooner it should happen, so thanks for taking the trouble to submit a request.
