Great Support: (original Mail from Support)
I've heard back from my dev. team on this issue and have done further testing my self.

In classic forms the repeating section won't shrink smaller than it's initial size when configured on the form. So if you have hidden fields in the repeating section it will not shrink to compensate for the white space.

I would recommend using responsive forms where the repeating section does compensate for the white space created by the hidden field.

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Again...Looks like Nintex is not willing to fix Bugs
Regards
Andrea

ok, I will open up a support ticket for a bug you know about since over 1 year. Great to see how serious you take your Customer...

Hi Euan
Filling out a Form with a Smartphone ist not a big requirement for us. I would be glad if you would fix reported bugs that are open since month:

https://nintex.uservoice.com/forums/229406-2-nintex-forms-for-sharepoint/suggestions/5247348-repeating-sections-should-have-an-auto-size-Option

https://nintex.uservoice.com/forums/229406-2-nintex-forms-for-sharepoint/suggestions/6312218-improve-hidden-panels-in-repeating-sections

Cheers
Andrea

Hi Euan
We are using External Data Columns or repeating sections within repeating sections. With complex Forms, it is important for us to have a fixed layout rather than having floating around items.
Cheers
Andrea

Please fix first all bugs in the "normal" Forms and provide a propper solution to migrte to the Responsive Forms. Looks like you use the user for beta testing.

Hi Euan
Good to hear that you are working on this Feature. With Universal Form you mean the Responsive Form I guess. As this type of Form is not usable for us, this will not help at all. Please stop adding new Features only into responsive Froms.

+3 votes. A common question in the community that the only answer is either Javascript (and doesn't always work) or multiple lists (messy, and not always practical if the column in question is dynamic). Would be MUCH appreciated if it were simply an option within the Lookup Control, where the control parsed out the input value from the ID expression on the backend, and used that value to determine duplicates and filter accordingly.

This is a standard thing in InfoPath and one that shouldn't require custom javascript or multiple lists to achieve.

Here's a way to achieve it in the mean time -- https://community.nintex.com/community/build-your-own/blog/2018/03/24/a-1-list-approach-to-cascading-look-ups

But, yes, this is a much needed functionality.

Could use JavaScript to do this but then of course, that means I can't use responsive forms...as that doesn't have support for JavaScript

+3 Votes.

What you're asking for essentially involves promoting denormalized tables as SharePoint lists, which I agree with!

SharePoint sites may be stored in a relational database in the background, but for most users formal database training is not included as part of their jobs. This feature would really simplify lookup lists and reduce complexity of list associations.

That would be very helpfull. With InfoPath Designer you can easily achieve this

Agreed... This would be very helpful!

I was very disappointed on the List Lookup control could not remove duplicate options. It forces developers to have JavaScript to remove duplicates. At this point, Nintex form is worse than SharePoint Designer.

Again, I'm amazed this has not been implemented yet.

In InfoPath you can select an option to remove duplicates, but I cannot see any way of doing this in Nintex. This would be a great feature to be included

It has been 3 years now since these comments, and "future release" of unique look-ups and multi field based filtering is not yet in the product. Nice!

This is only partly implemented - still no unique values ability. Lagging well and truly behind InfoPath! Not every list can have a multiple cascade in SharePoint - hence the need for unique values.

A common question I've seen on the net and Nintex community forums is how to remove duplicate values from the List Lookup object - an option to do this on the form designer rather than resorting to hacking with Javascript would be a big help to many.

Hi Emily

Is the filtering on drop down to be available soon. We have many users requesting this feature for Nintex Forms for Office 365 but dont want to make a development investment if it is being avialable shortly?