Hello!
I've found a dozen or so articles about this issue BUT they all pertain to moving Issue Types between a Classic project to a Next-gen project. Unfortunately for me, that's not the case here. This is all happening within one project.
I've got a custom field within my Bug Issue Type named, 'Bug Description' (so that we can use default text to include a template for that field since you can't put default text into the System Description field).
When a user determines that Bug isn't the right Issue Type and they 'Move' it to a User Story, they're never prompted to map the contents of 'Bug Description' to something else within the User Story Issue Type and the data is lost.
Steps to reproduce -
Create a Bug and enter data into 'Bug Description'
Select 'Move' and leave the project the same but change the Issue Type from Bug to User Story.
At this point, finish the process and move the Issue. I'm never prompted to select a mapping for 'Bug Description' to anything within the User Story Issue Type.
Am I doing something wrong? Is there a way to make sure that the contents of 'Bug Description' are migrated into a field (ideally, Description) that exists within the User Story Issue Type?