I've seen similar requests, but more complex ones. I need a simpler and specific thing.
Currently, the checklists' items have two default status: To Do (after you create it) and Completed (after you check it).
I need a status "Doing/In Progress", between those two, just as the Smart checklist plugin in JIRA.
Custom status, as other person requested, would be really useful. But I consider my request a first version to this more complex path.