If you don't want to pay for software and just want a taste of window previews, there is a hidden native macOS feature. However, it only works within the app you are currently using.
If HyperDock fails on your macOS version, try these: hyperdock for mac
In the world of Mac productivity, there was a time when the Dock felt a little static. Users coming from other operating systems missed the "Aero Peek" and window management features that made multitasking feel effortless. Then came If you don't want to pay for software