From the "Add Issue" tab, users can access the “Add Issue” form. "Subject", "Issue Type" and "Priority" are required fields to add an issue.
Filling in "Category", "Version" and "Milestone" is optional, but if you want to add a response that isn't included, you can add an option by clicking the icon.
There is no limit to how many issues, categories, versions/milestones you can add, regardless of your plan.
At this time, there is no feature to add multiple issues at once.