is there a way to merge issue types

[jlasheff]

Over time we have become a bit sloppy with control over issue types and we now have several that mean essentially the same thing with slight variations in spelling.  Is there a way to merge issues types together?

[Peter Bengov]

You can use the bulk change feature to Move issues. Just make sure both Issue Types have the same scheme (field, screen) before doing the change in order not to loose any field values. 

More info: https://confluence.atlassian.com/jiracoreserver072/editing-multiple-issues-at-the-same-time-829092790.html#Editingmultipleissuesatthesametime-Movemultipleissues

[Nic Brough -Adaptavist-]

If you delete the ones you don't want, JIRA will ask you what you want to move all the existing issues of that type to.