Once a structure is defined, and sample data has been created & is in use on an asset, you cannot change the types of the structure properties.

Specifically, you can change the type in the structure definition, but no other part of Studio updates to the new type, and the type is not persisted into the .noesis/data folders, even after File -> Save All.

Repro:

1. Create a new Structure, "PrimaryStructure", and add a property to it which is a collection of ImageSource.
2. Create a second structure, "CollectionStructure", and add a property to it which is a single ImageSource.
3. Create sample data for "PrimaryStructure", and set the collection to several bitmap images.
4. Create a new page/usercontrol, and assign the sample data to it
5. Update "PrimaryStructure" definition so the collection is now a collection of "CollectionStructure"

Result:
Sample data remains unchanged (a collection of bitmap images), creating new sample data is still a collection of image sources, and backing data definitions are still of the previous type as well. "Save All" has no effect.