When searching for a solution, you may come across the name "Pin." There is a GitHub project called "Pin" that uses modern macOS APIs to keep windows on top. While the concept is interesting, it functions by capturing the screen content of a target window and re-displaying it, which can be resource-intensive and less seamless than a true overlay. Similarly, you should completely avoid any application or script that claims to use private "SkyLight" APIs or any other method that requires you to disable System Integrity Protection (SIP). These represent a significant security risk and are not worth the potential stability issues.
: For video content in Safari or Firefox, use the built-in PiP mode to create a floating video window that stays on top of all other workspaces. : The classic deskpins for mac link