In Scrum boards, the +Create button is shown. But not in Kanban boards, unless certain criterias are met, which is weird, let me explain:

There should always be a +Create button visible, and Jira CAN UNDERSTAND under which parent it belongs if the swimlane is by Epic/Story (or grouped by Epic/Story), etc. So its strange that it is not visible in such cases! (how can Jira not understand? also the columns are by status, so the new issue type status should be clear already!)