Ive created a multi store and would like to add a link on the main menu of my default store to my 2nd store. However, the Category always appends the .html file. Does anyone know how to achieve this
Do you want to add a direct link to the base url of the other store?
By default, Magento does not provide to add other root category URL.
So you need to call static block and add static URL for same.
Hope it will work for you.