A "mental checklist" refers to a list of things you keep in your mind to remember or consider. It helps you ensure that you have taken all the necessary steps or considered all the important points without writing them down. Full definition
Go through a quick mental checklist: have you attached the correct file? (inspiringinterns.com)
I have a whole mental checklist of safety, fun, visibility, ratio of nice to mean kids, unattentive parents or nannies and cleanliness. (crappypictures.com)
The same thing likely applies to those areas at the bottom of the frontal lobe which seem to have acquired the ability to maintain mental checklists and monitor progress on an agenda. (williamcalvin.com)