When the filed is made mandatory through Field Required Validator, it does not do not appear differently from optional fields in the screen.
Only when in the transition it prompts that xyx field is required.

Same ways when the issue is created from Confluence these mandatory field ( set from Field Required Validator) does not appear.

Suggestion
It would better to have this function appear on Jira side
https://jira.atlassian.com/browse/JRACLOUD-76479, so when issues are created it also shows these fields.

Workaround
1. Create a custom field>> Add it to the create issue screen then make it Required in the field configuration>>
2. Edit the project's workflow, add a post function(create issue transition) that will copy the value from the custom field to the Epic link field