If you are already using script there is no need to complicate the matter buy involving a webhook or an external server. Just extend your script to perform the creation of the new records automatically rather than using a button to kick start the process. I can't offer any more advice without seeing what script you already have so post a simplified version of it without unnecessary details.
There is a big misconception about webhooks. First of all they are not really a "thing" - there is no web standard or API for webhooks. It does not exist. They are just a marketing term / buzz word for URL endpoint and set of parameters established by convention that can be used for mostly unidirectional communication between two web services. And in the context of QuickBase webhooks work best when communicating between QuickBase and external service (rather than QuickBase to QuickBase). A QuickBase to QuickBase webhook can only react to a very limited number of events related to records but a script can react to thousands of different events.
Also, what do you mean by "there is no relationship between T1 and T2"? Which table is the parent and which is the child?
