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What seems like an eternity ago, I made another feature request that might make this a simple matter to deliver: https://community.cireson.com/discussion/1378/outlook-add-in-open-portal-forms-instead-of-console-forms
The JSON text files that define a portal form are several orders of magnitude easier to customize (such as required/not required, disabled, layout of fields, etc.) than the XAML forms.
I leave it to those more familiar with the inner workings of the product to determine whether this makes it easier or not to deliver, and to those who voted or will vote on this FR to decide whether that way of configuring which fields are required is acceptable or if you really want some kind of GUI form instead. Again, these are not duplicate FRs, but everyone gets to decide if they are complimentary, with their votes.