You can enter Custom URLs for the Home Page but you can't do anything with the New Tab page.

I agree you should be able to. You may want to suggest it as an "Idea" at: https://connect.mozilla.org/t5/ideas/idb-p/ideas

You can enter Custom URLs for the Home Page but you can't do anything with the New Tab page. I agree you should be able to. You may want to suggest it as an "Idea" at: https://connect.mozilla.org/t5/ideas/idb-p/ideas

This is so sad. This should have been by default.

But anyways, I have posted it as you said, and here it is.

https://connect.mozilla.org/t5/ideas/how-to-change-home-page-and-new-tab-to-desired-url-or-any/idi-p/74522#M40174

Consider upvoting so that Firefox team brings this revolutionary feature very soon.

These are you options for setting a home page or alternative url.

"How to set the home page" https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

"How do I set a different home page and home button." user post help. https://support.mozilla.org/en-US/questions/1341696

These two help links should help set homepage and new tab "homepage" but for extensions you can't change those are the Addon creator don't give you permission to change or modify their software.

As of now, I am using this addon, Bonjourr · Minimalist and lightweight startpage

https://addons.mozilla.org/en-CA/firefox/addon/bonjourr-startpage/

This works but something in-built would be beneficial.

Unfortunately, beyond the Firefox help on Homepage and New Tabs help that is all they have and beyond that would be a Addon or 3rd party software to do what your asking.