I'm trying to create a website builder (drag and drop page builder) and was wondering where to store the styles when someone changes the styles of an element. For example, in WordPress you can type in your own custom CSS in Customizer (image example: https://i.imgur.com/qaUiVl6.png)
In other page builders like Wix or Google Chrome Inspect Element, you can click button to enable or disable styles.
While making current/live CSS edits to the page, where and how are these styles saved? (I'm not talking about a database as the code has not been saved yet. I'm talking about while making changes onsite changes, where do these "temporary/live" CSS styles get saved?)