1. With the Todo List open with v. 18.0.1 of the mod (Factorio 1.0.0, naturally), save and quit the game.
2. Update the mod to 18.0.4
3. Open the saved game.
4. The open todo list will be stuck open, and pushing the button that opens it opens another new version of that window instead (it seems the layout was changed a bit in 18.0.4). The result looks like this: https://imgur.com/a/pkWkp4A

The left window of these (the old one) is impossible to minimize in any way - the Minimize button on it minimizes the right (new) one instead.

The solution to this was to downgrade the mod back to 18.0.1, open the save, minimize the window, save and quit again, and then I updated to 18.0.4 without any issues - it's the window being open in the save that causes the problem. Still, it was rather annoying, and I hope for a fix so that anyone else updating doesn't go through this.

(I got this bug on a modded playthrough, so it's possible it's caused by something else, but it's probably just related to the todo list layout change from 18.0.1 to 18.0.4)

Hey, thanks for this report.

This is definitely caused by the changes I made yesterday.

I’ll create a fix.

Should be fixed.

Thanks for the detailed report :)

Haven't checked if it happens now, but thanks for your work! You can close the thread now or something if you want (I don't know if that's normally done on this portal).

No worries :)
I just ignore it until it disappears to the bottom :D