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 from the current version 0.2-beta.2
Sort doesn't work
Sort settings are not respected on a View with multiple joined forms.
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.
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.
Merge Tags from a joined form can't be used.
It's not yet possible to use Merge Tags from different forms inside a single Custom Content field. The Merge Tag for each form can only be used inside the Custom Content field of that particular form.
Advanced Filters support
Only fields from the main form are supported on the Advanced Filters
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:
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: