Summary
When you add a new custom data type to top-level collaboration this data type is not available in different places in DataType selectors.
Other way around this works, e.g. Add to process variables/Imports first and then use the custom type.
For Correlations on actual nodes the data and message types expressions contain this custom type from top-level Collaboration.

AC
IF I add a custom datatype in collaboration sections it should be propagated in other datatype selections.