Board Thread:The Quarters - Q & A/@comment-71.94.249.114-20171023165311/@comment-25085701-20171026181454

There's also another little-known workaround for this:  create a challenge with the to-do in it; when you leave a challenge and rejoin it, you get the challenge items added to your to-do list. So at the beginning of a month, you can just reset the challenge.

Granted, I haven't tried this since the latest update...