TaskPaper 3.5 seems to be a whole new app in Mac App Store with no ability to upgrade from previous version. Also I can’t run previous one on Sierra. Do I need to buy it again?
Yes TaskPaper 3 is a paid upgrade. There’s a 50% off upgrade discount if you owned a TaskPaper 1 or 2 license.
More information upgrade discount is here:
More information on why TaskPaper 2 stopped working on Sierra is here: