After researching the community forum I haven't been able to find a use case that quite matches what I'm trying to do.
Use Case
I have a single work item type associated with a single workflow. There's a transition between my Being Planned status and Waiting for Approval status. Some fields are always required, which I've specified in the transition Validators. This part is working well as-is.
Some fields, however, are conditionally required when the corresponding custom field is set to a specific value. For instance, when my field 'User Notification Required?' is set to 'Yes', then make field 1 required, otherwise field 1 is not required.
Question
Is it possible to prevent a user from transitioning an issue based on my use case? Please note I'm only interested in using Jira native functionality (please no 3rd party apps).