Custom checkbox or button in order page to increase stock when sending out a quote

I have a very small "start up" WooCommerce shop and I work on commission requests, 50% of the store is commission based the remaining 50% is normal sell.

Commission builds are always set with a managed stock of 0, so each of these items are always "out of stock".

I use another plugin to place a an "Product Enquiry" button (one of the Request a quote) to have clients communicate a request and this button is configured to appear with items that are out of stock on purpose. (Obviously commissions never exist until built)

I then send back a quote email that has an "Accept" link which directs them to the cart so they can check the contents before proceeding to the checkout page.

I am looking for a way to automatically increase the stores stock level by the products listed in the quote and their quantity in the to match the request, directly via a checkbox in (for automation) or a button in the order page before I send the quote.

I have searched many days and hours for a code solution or a Plugin => Nothing. It seems most peoples shop models want to do the opposite..

I have tried multiple options and code that I place in a plugin so I can activate and deactivate for safety.

I am now banging my head against the wall, because sometimes; being busy I forget to increase the stock level before sending the quote to allow the client on clicking the "accept" link in the quote email to enter product in to the basket.

As you know it will bounce the client if not elevated (with a message " sorry you cant add out of stock items in to the basket".

I believe WooCommerce once used to have this button in the orders page but it is now not there, I am on Woo5.6.0, WP5.8 and PHP7.4

Do you have a PHP code snippet solution to add automation say a checkbox in the order page or bring back the stock increase button before sending out a quote ?

Thanks.