How to update records between two tables and two cross linked apps with no relationship

I have created a parent app and a client app. The client app is open to the public

The process is this....

• Quote is created in the parent app and through Actions, I am creating a new quote approval request in the client app
• The record id# of the quote in the parent app is being copied to the client record as the Quote ID# and this field has been made the key field
• When the quote is created in the client app, an email is generated to the customer with a link to the quote, particulars about the quote and two fields which are Click to Approve and Click to Decline.
• This is passing information back to the client record that the quote is approved or decline

Now the trick.....

• Since the tables are not linked through a relationship and only app cross linking, I need to pass the response back to the record in the parent app and change the Quote Status

Two questions....

• Is this a function that a webhook can accomplish or am I missing a step of creating a relationship between the tables and simply us an Action to accomplish this without a lot of coding (my weakness)

My goal is to keep the two apps separated from each other as much as possible due to the use of a Public role and to limit the potential for access to our parent app and security issues