I have a new project where I want to track QA specialised activities. I have created a number of new issue types - for example: Test Request. There are cases where more than 1 QA would be working on any given ticket.
What I want to do is enable the ability to create sub-tasks under those new issue types or if that fails, I would like to use some of them as "Epic" like tickets that could have child tickets assigned to different QAs.
I cannot manage to find where I can enable sub-tasks for specific issue types and/or change the hierarchy of the ticket and make the type "Epic" like.
Additionally, I have a company-managed project so that I could pull in tickets from other company-managed projects for visibility.
The only place where I could find hierarchy is here: Issue type hierarchy. But I cannot seem to edit this or add more than Epic to be on that level 1. (I'm the system Administrator for Jira)

Can anyone help with either or both of the above?