How to make new advancement pages?

Yes you can, you can do it by going into the "Resources/Data/{mod name}/advancement" and adding a new json file of a advancement that has no any parent attached to it.

you can use this website to make it easier to make new advancement without going through json creation.

https://misode.github.io/advancement/

also you'll need to have the criteria to be able to get it, without it the player wont be able to unlock the menu for example.

if you want the player to gain it if they place a block, use a "any block use" trigger or if you want the player to have it on the get go then use "tick"

if you want to make advancement that is attached to the menu, just make the id parent to "{mod id}:{the file name of the advancement that you want to connect}"

(do note if you're doing this i think MCreator will not show it as a option for procedures but you can learn how datapacks work)