GroupShelf groups windows from any Mac app into tabs, like browser tabs for your whole desktop. Hold Shift and drag one window onto another to make or join a group. Move or resize one window and the whole group follows. Pull a tab off to split it again, color your tabs, name your groups. Native and lightweight, for macOS 15+ on Apple Silicon and Intel. $9.99 one-time, with a 30-day free trial of every feature.