Known limitations of Multiple Forms
The Multiple Forms plugin is still in beta, which means that some native GravityView functionalities that usually work on a simple View still don’t work on a View with multiple joined forms.
Here’s a list of known limitations as of version 0.7.0.
1) Filter conditions currently reach only the primary form’s fields
As of Multiple Forms 0.7.0, Advanced Filtering conditions reach only the fields of the View’s primary form. The condition builder lists those fields, and a condition pointed at a connected form’s field does not match, so a View cannot currently be narrowed to the entries that have no matching entry in a connected form. On a union View, every row is a standalone entry, so conditions apply through the primary form’s mapped columns. To learn how unions work, read Using unions in Multiple Forms.

Two things do work across a join. The “Strict Entry Match” View setting decides whether entries with no match in the connected form appear at all, and the Sort Field setting accepts a connected form’s fields, listed with that form’s name and ID.

Sorting ascending on a connected form’s field therefore groups the entries that have nothing in it at the top of the View, which is the closest thing to a list of what is missing.

2) Can’t specify fields for editing
Since each joined form has its own link to edit entries, it’s not possible to specify which fields can be edited. The Edit Entry tab must be kept empty for entry editing to work.

3) The Edit Entry link must link to each form
If you wish to allow entry editing, a link for each form must be added to the View.

4) Merge Tags from Joined Forms
It’s not possible to access or use Merge Tags from other joined forms inside a Custom Content that belongs to a specific form.

You can still include data from joined forms, but you must add a Custom Content field from that other form:

Additionaly, the merge tag selector will only display fields from the main form and you’ll need to manually type the merge tags for the joined form fields .
We understand this isn’t very intuitive, and we’re working to improve the editor’s usability in future updates.
5) Merge Tags on the Edit Entry tab
Merge Tags added inside a Custom Content field on the Edit Entry tab won’t be parsed.

Result:

6) Impossible to edit Nested Form fields
GravityView supports editing Nested Forms fields, but if the View has a joined form, editing a Nested Form field doesn’t work.

The Edit Entry page on a View using Multiple Forms:

7) It’s not possible to specify a field from a joined form in the Search Bar
While it’s currently not possible to add individual fields from a joined form into the Search Bar, the search will work if the “Search Everything” option is added to the Search Bar widget.

8) The Maps layout isn’t supported
There’s no way to display a marker on a Map layout from an Address field coming from a joined form.
