The thinking behind the current behavior is that you check off the actions in the project or group, and then the project or group appears so you can check that off, too.
That said, I believe we've gotten a feature request for something like this; would be useful to email the
support ninjas so you can be attached to that request. Thanks!
In the meantime, you could always add the checklist as a note - that way you'd have it for reference, while only seeing a single item in your list. Hope that helps!