You want to reduce the number of items passing through the flow?
Then you can only do this with an IF node after this set for example.
Or by creating a new itemlist with the code node.
something like this:
// Loop over input items and add a new field
// called 'myNewField' to the JSON of each one
const newItems = [];
for (const item of $input.all()) {
if(item.json.profile.email!== undefined){
newItems.push(item);
}
}
return newItems;