Is it possible to manage your plans in hour unit?
No. WBS Gantt-Chart for Jira only accepts a date unit.
Since the feature is not available at the moment, we have a suggestion raised for our development team on our Productboard and can be checked at the URL below:
In order to receive updates regarding the feature, please vote for it by clicking either [NICE-TO-HAVE] or [IMPORTANT] or [CRITICAL], enter your feedback and Email address, then Submit.