There is still no built-in way to disable predefined browser shortcuts. Pages can preempt many of them, but not Ctrl+T. If you haven't already, you can vote for this "idea" on Mozilla Connect:

https://connect.mozilla.org/t5/ideas/customizable-hotkeys/idi-p/4979

Meanwhile, did it just break in Firefox 137? If you know the version, that could be helpful in tracking down the updated code.

If you check the Browser Console (Ctrl+Shift+J) right at launch, is there any error message related to the startup script?

Not sure when it broke. I package a Firefox browser that is locked down to only surf an application site.

See the attached image on the console error.

What I like to achieve is ctrl-T to open a specific page but I believe you removed that feature as well

The error is on line 2, character 20? Did you already make the modification in cor-el's last reply in the other thread?

https://support.mozilla.org/en-US/questions/1367908#answer-1602261

As for setting a new tab page programmatically, there was a change for that recently because a file was renamed. See, for example: https://www.reddit.com/r/firefox/comments/1ikvt8s/fixed_firefox_136_breaks_local_file_as_new_tab/

Thanks I tried using

const Services = globalThis.Services || ChromeUtils.import("resource://gre/modules/Services.jsm").Services;

Now I get it cannot find ChromUtils now as attached

I am confused what the rename file is? I think the new name is just the filename defined in Firefox64\defaults\pref with prefs

pref("general.config.filename", "config.js"); pref("general.config.obscure_value", 0);

If I open the Browser Console (Ctrl+Shift+J) and run this line

const Services = globalThis.Services || ChromeUtils.import("resource://gre/modules/Services.jsm").Services;

I don't get an error message. So I'm not sure why you get an error message having that in your startup script.

That is beyond my knowledge.

I am confused what the rename file is?

The file name change is related to the code for setting the new tab page through a startup script. The file named changed from:

AboutNewTab.jsm

to:

AboutNewTab.sys.mjs

Please refer to the previously linked thread for more information.

im still getting ChromeUtils is not defined or Components not defined either trying

var {classes:Cc,interfaces:Ci,utils:Cu} = Components;

/* set new tab page */ try {

 Cu.import("resource:///modules/AboutNewTab.jsm");
 var newTabURL = "file:///C:/startpage/index.html";  
 AboutNewTab.newTabURL = newTabURL;  

} catch(e){Cu.reportError(e);} // report errors in the Browser Console

or

ChromeUtils.defineESModuleGetters(this, {

 AboutNewTab: "resource:///modules/AboutNewTab.sys.mjs",

});