Freeplane - Freeplane is a powerful and free software for building mind maps.
Witch - Welcome to the world of W. i. t. c. h.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Hyperswitch - HyperSwitch provides a compelling alternative to HyperDock for keyboard junkies. What's New
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
Contexts - Switch between application windows effortlessly — with Fast Search, a better Command-Tab, a Sidebar or even a quick gesture. Free trial available.