There is no save because clicking OK saves any changes you've made in the editor.

As for the error... if you're getting it immediately after loading it on windows 7, it usually means you've not installed all windows updates.

If you check the foobar2000 console from the View menu, you might see one of these 2 errors

This component requires a system with IE9 or later. << I don't really need to explain what is missing. Windows 7 users really should have IE11 installed even though it's functionally useless and you must be using another browser to browse the web right now!

Critical graphics initialisation failure. << This means you've not installed the windows 7 platform update. There are special instructions with a link for windows 7 users here... (edit: thinking about it, you wouldn't see the javascript error text if this was missing!!)

https://marc2k3.github.io/jscript-panel/docs/#minimum-requirements

If you have these requirements installed then any errors would be due to a bug in the script you're using

Here's an example of me using it on windows 8.1 (the oldest OS I have access to right now)...

I'm pretty sure you can update IE without SP1 so that should be easier.

• The netbook I'm using for this runs Windows 7 Starter (32-bit) with IE8 (I actually use Chrome for web stuff, when required), and first I took a system image so I had a chance of reversing any damage.
• I had previously installed FontAwesome (see https://marc2k3.github.io/jscript-panel/docs/#minimum-requirements).
• I downloaded the IE9 installation file from here: https://www.techspot.com/downloads/5047-internet-explorer-9-windows-7-32bit.html, having first checked it for malware here (which lets you provide the download link, then runs the payload past a huge list of malware checkers): https://www.virustotal.com/gui/home/upload.  (Good luck if you try to get an official IE9 download from Microsoft!)
• Running the IE9 installer complained that the OS needed an update (which got me worried), but I followed the KB (Microsoft Knowledge Base) links and found it was a minimal update which completed quickly.
• After the update, the IE9 installer ran (with the Wi-Fi turned off by now, so I could tell if it was trying to download anything else).
• In FB2K (v1.6.11), I uninstalled the current JScript Panel (v3.0.3) and installed v2.8.8.  As discussed in previous posts, v3.0.3 requires Windows Platform Update, which itself requires SP1... and I'm not sure Win7 Starter is even a candidate for SP1!
• I am now able to run the sample scripts provided in v2.8.8, of which I am using the "JS Smooth Playlist Manager" script, within a tab using the DUI.  The script editor window does not have Save and Exit (etc) buttons at the bottom due to the 600px height of my netbook screen, but the workaround is to use Ctrl+S to save and the top right X to exit.

Just in case anybody else follows this path:

window.SetProperty("SOME.PROP", VALUE);

on_property_change(prop_name, value) {
    // do something
    // or sync property with other panels
    window.NotifyOthers("propUpdate", {
        prop: prop_name,
        val: value
    });
}

var colour = window.GetProperty("COLOUR", RGB(0,0,0));

function update_colour() { // triggered by clicking a button/menu/whatever
   colour = ...
   window.SetProperty("COLOUR", colour);
   window.Repaint();
}

function property(name, default_) {
	Object.defineProperty(this, 'value', {
		get : function () {
			return this.val;
		},
		set : function (value) {
			this.val = value;
			window.SetProperty(this.name, this.val);
		}
	});

	this.name = name;
	this.default_ = default_;
	this.val = window.GetProperty(name, default_);
}

var colour = new property("COLOUR", RGB(0, 0, 0));

gr.FillRectangle(0, 0, 200, 200, colour.value);

colour.value = some_new_colour();

"strong texture"??

I may consider letting people choose the font/symbol used via the properties dialog.