Hey, You can go to Options>>Home then choose from "Homepage and new windows", you can set another url as homepage or a blank page.

of course. I am aware I can do blank/firefox home/custom homepage but this wont give me the option to set a 'new tab extension' like momentum or tabliss

I tried adding 'Momentum' and works fine with me. After giving my name and mail id, whenever I click on a new tab momentum extension kicks in and provides me with the default momentum new tab.

the option wont show up before (and for tabliss extension) but momentum works