How to freeze and unfreeze the basket when placing an order?

Question

Online shopping

The user walks through my online store, has already put something in the cart and goes to the checkout page. And he also has other tabs of my online store open. And here he is, filling out the checkout, did not finish and on the "product" tab clicked add to cart.
What is the correct algorithm of actions in this case should the store have?
1) In the simplest case, it will update the checkout page and new products will appear there and the price will change. It's right?
2) If not, then you need to put the cart aside during the checkout process, giving it the status "frozen" - that is, it cannot be changed. So?
But, then the question arises - what to do with the current / new user's basket if he entered the basket during the checkout process? Or even left the site and then returned after 2 days.
Show her the same - confused? Or clear frozen and show a new one? It seems wrong to clear because the cart is only cleared when the user has clicked on "pay".
Then what to do?
Let's say that I even reserve a frozen basket for an hour on a timer. What to do in an hour? If the frozen cart is cleared, and if the user has already put something in the new cart at that time, where will the goods go when the old empty cart becomes unfrozen?

Answer 1

You need to display a warning that an order is already being placed in another tab and this process has not been completed. And options to choose from. What are the options, already think for yourself. For example:

1. Add a product and recalculate the cost.
   At the same time, old goods can be canceled altogether and, as it were, switch to the mode of replenishing the basket from scratch or not.
   After adding, you can proceed to design, or you can stay in the catalog.
   
2. Do not add a product and proceed to checkout.
   
3. Create a new order, separate from the one that is placed in another tab (new separate basket).
   
4. Set aside what you want.
   
5. Etc.