[Question] Can I add additional parameters and if yes how to do that? | Change main container in checkout page?

[Sztacho]

HI. I try to make my own shop. But I need to add middleware or something like this to add additional parameters to SF. I'm new in VTEX and I have known only how to create a shop and how to edit a little checkout page. Moreover, I will know how to customize the main container in checkout. Someone can help?