I am working with the Quick Report Template and have a couple of questions about the Add Details/Attribute Pages.
I am going to share this ArcGIS Learn lesson, https://learn.arcgis.com/en/projects/use-arcgis-appstudio-to-build-a-311-mobile-app/ and this youtube video regarding Quick Report, https://youtu.be/SkduFWI-9EQ
So the way it works is, Quick Report template will get the list of attributes and its type from the feature layer, and dynamically create the question in the Add Details page, so if you want to add more questions to the Add Details page, you should add attributes to the feature layer and set the type appropriately. (And don't forget to click Settings>Reset on the app after changing feature layer or adding/update attributes to the feature layers)
For a "drop-down" type of question, you need to set the coded-domain values for the attribute that you want to have it shown as drop-down question as shown in the City of Cilantro 311 App. Look at the feature layers that are used and they have coded-domain values, https://services2.arcgis.com/j80Jz20at6Bi0thr/ArcGIS/rest/services/Cilantro/FeatureServer
I hope this helps,