I don't. I'm a software developer in my day job and during that I need to keep my ADHD in check with task lists and tickets...

So whenever I play I pick up something that looks fun and roll with it... if I forgot some plans midstream then I just let them go and do something else.

I, specifically, never want a TODO list item that I'm not looking forward to to be hanging over my head - because then I'll never pick up the save file again.

That's one way!

You can also add map markers to your map, with an icon and text. I've used these to set goals / reminders of what should be worked on in that area.

My general method to remember what I need to do next session is to name my saves that way. Like "start coal depot.sav", or "finish steel, fr this time, no distractions.sav".

I've been using a signpost mod for many years, along with a todo list. Especially valuable for complex mod plays like an angel and bobs run

Last night my in game alarm went off for low power. I was about to fix it, so I muted it. But then I realized I was done for the night, so I turned it back on, saved, and exited.

So there is no way I forget what my next task is.

In my prime time I had a database of everything (yes it was access and no, it wasn't good)

I use a kanban, or you can make notes with the in-game displays

https://gokanban.io/

Or a Google doc, or just a paper on your desk with notes. :)

I've often thought that Factorio needs a comment block / sign post / notepad for just such a thing

I often leave my reminder on a post-it note on my monitor. Sometimes those get lost and then I have to depend on my own memory (dubious)

Recently I was in the middle of fixing up a facility that wasn't working right when opposite sides of my base got hit hard by bugs. They broke through walls while I was travelling to repair the first attack, just a mess all around.

Anyway, I decided I didn't want to deal with the cleanup right away because it was already getting late, so I left a sticky note. Then it took me a couple days to get back to the game and the note went missing. I remembered to clean up and shore up the defenses, but I forgot that the thing I had been working on before the attack wasn't quite finished. Came back to it a week later to see why my resources weren't getting shipped before I realized what happened.

Most games don't seem to let you name saves anymore, but I used to name my saves after whatever I expected to do next.