NotePlan is a great productivity scratch pad. If you're familiar with the analogue Bullet Journaling system and have been seeking a digital alternative this may be your best bet.
I tend to use this to dump and organise my thoughts throughout the week and look back over them during a weekly review. It keeps unnecessary junk out of my task manager (which is 2Do, just in case you care). From there, you can decide to cancel, complete or schedule the tasks using its hybrid calendar/text file interface.