Currently I am unable to import issues more than 250 using Issues -> Import issues from CSV (enabled for all users), when I went through existing queries found one more way to import from Advanced Settings -> External system Import and was successful in importing all issues. Looks like External System Import is enabled only for Administrator users and not for all users, can you let me know how to enable External System Import option for all users?
Also I found that jira.bulk.create.max.issues.per.import key is used to set the maximum limit to import via CSV to the users. Let me know if setting this key will allow all users to import issues more than 250 from Issues -> Import from CSV or not. If yes, currently this Key configuration is not available in System -> Advanced Settings, kindly let me know how to set this Key configuration.