One solve for this is to use a variable for your to_date.
1. In your load script, set a variable
LET vToday = date(Today(),'YYYY-MM-DD');
2. Leave the connection query parameters as you have them and then change the query parameter in your load script by using the WITH CONNECTION function which will override what you have stored in your connection:
FROM JSON (wrap on) "root" PK "__KEY_root"
WITH CONNECTION (
QUERY "to_date" "$(vToday)")