This is a great mod, but it is a little irritating to press escape when I want to close the gui only to remember that you have to click the icon.
The “Confirm window” control or the “Toggle menu” control could be used.

When I was making the mod, I was thinking about whether or not to do it and couldn't decide any one way. The ability to have the mod's GUI open at the same time as other windows seemed worthwhile. Do you think there really is no need of that, or not enough to outweigh the drawbacks?

I usually use the mod by making a template in one sitting, then leaving it closed for a comparatively long time. I can't see a situation where I would need to have other GUIs open at the same time, especially considering how much of the screen (more than a quarter) the Default Wait Conditions GUI uses.

Thanks for the feedback, I'll try to get it done in near future.

When you get around to it, I think it would also be nice to have a square button like other mods just for consistency.

I also realised that you can have the GUI open at the same time as other GUIs if you have a little X in the corner. Here is an example of a mod that does that: https://mods.factorio.com/mod/Blueprint-Editor

Or, better yet, an option to move the button to the toolbar rather than the corner.

What button do you mean by "a square button"? The toggle button is square as far as I recall.

I can add an X button, although it's not as simple as it seems. If I do so, I may add a setting for whether to close the window on E.

I have an intense dislike of shortcuts (and the toolbar's position in general) due to them obstructing the vertically limited field of view. I don't see myself adding one unless there is an extremely convincing reason to do so. You may have better luck looking at https://mods.factorio.com/mod/GUI_Unifyer for this.

"What button do you mean by "a square button"? The toggle button is square as far as I recall."
Apparently my save had saved a rectangular button: making a new save has a square button.

I also don't see the fact that you won't use the button on the toolbar as a good reason to not add it.

Apparently my save had saved a rectangular button: making a new save has a square button.

That's interesting, considering it has never in the mod's history been rectangular.

I also don't see the fact that you won't use the button on the toolbar as a good reason to not add it.

It doesn't matter if I will use it or not. I am ideologically against it. You won't be willingly engaging in, say, racism (I assume you are against racism), would you? Perhaps it helps if I put this bluntly: fuck shortcuts and whoever decided to put them where they are. I'm not having that shit in my mod.