I like it way more than other Task List / TODO List mods I've used before!
I am able to help with the code for some, but I don't have Factorio modding experience, I'll learn by helping you, if you agree of course. So I'd also appreciate a review in PRs I submit.

Some feedback, mostly on QOL but other categories mixed in:
- I loaded into a preexisting save, and I was expecting to see a group for each planet I was already on, being that groups are the selling feature of the mod
- Also leaning on groups are the selling feature of the mod, it is too cumbersome to add a group. I'd appreciate a quick create button, with just name and icon (leaving position to the group management window). Maybe this could be turned off from the settings when I have my groups set and don't want to see the button
- Could be more condensed to not waste space when permanently pinned. I've seen other mods implement a small folding icon alongside the close button. This could toggle between compact/detailed view
- It is still too easy to complete a task. It would make more sense to me if clicking on the name would expand/show subtasks instead of completing
- "add to top" apparently not working for subtasks

It would also be amazing to have a groups synced with map view, so that when I go to Fulgora, I see the list I've set for Fulgora. I know this is not the only way to use the mod but I think it's a common enough way to perhaps have an optional feature?

I understand these are all highly personal to me, and not everything will be implemented, I'm just voicing my feedback :)

Thanks for the feedback, I definitely still have a lot of QoL features I can add and these are great ideas!

I would love the help. It took me a bit to get used to lua and factorio modding but the good news is you only need to focus on user interface stuff.
I have saved links that are helpful for me on the Github repo. I recommend working through Claude Metz's UntitledGuiGuide to get used to modding in Factorio, (and in between chapters experimenting with either adding new things by reading the documentation, or experimenting with interactions).

Oh, I realized you said you wanted to learn by helping me so while I recommend going through the guide if you do want to start work on implementing one of your suggestions, just make a draft pull request, and if you get stuck you can always ask me for help there. (Understanding other people's code is always challenging).