Create a folder, put markdown files in it, sync* and backup* the folder however you like and edit the files with whatever you like*.

Within my folder I have a daily journal - start each day with a list of what I hope to achieve today and make notes throughout the day as I progress on those tasks. The next day that journal becomes something I'lll refer back to in the morning to decide what to do next. Depending on the project - weekly or monthly might be more suitable than daily. Or maybe something else entirely.

I also have folders an files for longer term tasks.

If you want to collaborate, make a second folder and choose a sync platform you can all agree on.

(* I use GitHub for Sync, Backblaze B2 for backup, and Visual Studio Code for editing, with extensions for markdown and making GitHub a little easier... specifically GitDoc for auto-commit/push/pull and Markdown All in One for formatting/etc. Also Copilot is handy for some note taking tasks. The "foam" extension mentioned here looks like it might be great too)