Aight,
sorry for the delay got called back into work for 14 hours.
you would need something like this.
Im using the “make Api call” module because it returns in a more usable format that costs less
make operations to modify
/v1/blocks/<your-page-id>/children
Do not use a notion database template, that is still not supported by the notion api. use a regular “dummy” page as the template.
^^you will want to do this with an array formula instead of what I have done here in more complex scenarios, (apologies) this is a little sloppy.
notion wont automatically update the variables on the page, you have to do that with formulas in
do make sure the object is back in the expected format (an array of collections) when you plug it back into the the append content module.
I can elaborate more later if you still need help, but thought id get this over to you before i get sucked back into work 
and another day goes by.