Hello, as Shane mentioned it is not possible to save a few fields in a single incomplete Form. Without submitting the Form, those entries will not be stored anywhere and progress will be lost. On the other hand, it is possible to create an incomplete post by submitting a Form with fewer input fields. Then you could edit the same post in other Forms, showing a few different input fields in each Form, breaking up the post editing process into multiple Forms on separate pages. This could make front-end editing of Cases complex, but it is possible.
Let's assume each Case post has 30 input fields. You could place 10 of the fields in the first Form, which is configured to create new Case posts. Ideally you would capture the main critical information, like post title, in this Form. You could set that Form to create posts in "Draft" status if you don't want to publish the Case post until the User has filled out all the fields, or you could publish the post immediately in an incomplete state.
After submitting the first Form to create a new Case post, you can redirect the User to the second Form, containing the next 10 input fields. At that point, the first 10 inputs would be saved and they no longer need to be displayed on the second Form. Only changes to inputs 11-20 would be considered in this Form. The second Form should be configured to edit the existing Case post, and retain the current post status upon submission. After submitting the second Form to edit the existing Case post, fields 11-20 will be saved, along with the existing fields 1-10, for a total of 20 fields saved in the Case post. Then you could redirect to a third Form configured to edit the existing Case post, displaying fields 21-30, and set the post status to Publish when the Form is submitted. At that point, the User has had an opportunity to fill in all the fields, and it probably makes sense to publish the post.
You'll need to consider the workflow when a User abandons the site without completing all the stepped Forms. Do you want their post to be published, or kept in draft status? If they leave the site and return a few days later, they may not remember the Case post was incomplete, so you might need a way to direct the User to edit their incomplete Case post(s). When they try to edit the Case post, it might not be straighforward to determine which step they should return to. The User can skip through any completed steps quickly, since any existing field values will be shown in the edit Form.
Assuming you create the Case post initially in draft status, you might also want to decide how to handle post edits after the Case is complete. At that point if the User wants to edit the Case post using Forms, you would have to decide whether you want to show a single Edit Post Form with all the input fields, or if you want to show another stepped Form where there are just a limited number of input fields per page.
Your thoughts?