make a mental note
To make a special effort to remember something in the future. I must make a mental note to pick up the dry cleaning on the way home from work. Jenny, make a mental note of this number and remind me to call it when we get home.
make a mental note of something
to remember something. So, you want to be considered for a job. I'll make a mental note of that. Please make a mental note of my telephone number.
make a mental ˈnote of something/to do something
make an effort to remember something without writing it down: I must make a mental note to order more wood.She made a mental note of the car’s registration number.