@Pesala Thanks for your reply.
I surely know that I shouldn't close my named stack. Let me clarify a bit about the steps that I mentioned before.
See the following example:
I have the original workspace (Workspaces) and another workspace called, e.g., "Travel".
In the workspace "Travel", I open several tabs and group them to form a stack, e.g., "hotels".
Then I go back to the original workspace (Workspaces) and close the tabs in this workspace until the browser window disappears (but remember that the application is not yet closed on Mac).
Open a browser window again.
I expect that the "hotels" stack in the "Travel" workspace might have been retained even though I do something else in another workspace. However, as I said in the previous post, the "hotels" stack becomes unnamed after I open a new browser window, which is undesirable.