Nice and simple app, really user-friendly. However, I had to dig on the internet to figure out how to use an already existing tasks list, coming from Thunderbird. It's not too tough to do with the instructions found here: https://dbfin.com/linux/synchronize-thunderbird-calendar-events-and-tasks-with-gnome-shell-built-in-calendar-via-evolution/. Speaking of online accounts, I have my google account set in the account manager and its tasks list appears in this todo app as soon as it's open. But here comes the troubles: each time you want to modify or delete a task, even if you scroll down the list, an error message appears (saying something is read only blah blah). The problem is not that you can't modify or delete a task, since these commands do their jobs, it's just that the closing of all these error messages (by the x at the top right corner) takes quite a while and dramatically impacts productivity. I didn't try other tasks lists from other accounts. Still it is a good app if you stick to your personal tasks list on local drive.
It perfectly does what it is supposed to do. A simple, down to the earth task manager for those who do not need complex task managers with lots of options and possibilities. It takes a little while to find out how it works. A small manual of one or to pages would be nice.