Suggestions

Permitir crear subcategorias, y que al completarse todas se complete la categoria principal

I think that a to do list is a lot more fun when you can have a little bit of customization (please add Annie Use Your Telescope!!)

It would be nice if there was a feature to adjust the color of the font and the backgrounds etc.

Just dark mode

It would be cool to just drag and drop lists to rearrange them into a different order on the side bar

The user may want to write some job inside each item that he want to do as example if i am going to study English so inside it i want to write that i want to study reading, writing, grammar and vocab and add a check box for each item

I have a suggestion that you recomend to the user if he want to reorder the list by ai if he do not know what to start with

I think adding colors would add more attraction to your site............................

Able to change the tasks between horizontal and vertical mode.

Have a comment chat bubble icon next to the Tag icon. You click it and it opens a lightbox that lets you add a comment. First 50 or so chars of the comment could show in grey text on the main display / row alongside the task name, and you can hover over icon to see all the text in a tooltip if there is more. Or click the icon again to see it all and be able to edit it in the lightbox.