CheatSheet is lets you view available keyboard shortcuts in your current application. Just hold the ⌘-Key a bit longer to get a list of all active short cuts of the current application. It's as simple as that.
Pretzel is Mac desktop app that shows and find keyboard shortcuts based on your current app.
Adele is an open source repository of publically available design systems and pattern libraries. Adele lets you browse systems by technology, data structures and parts of systems quickly providing insights and inspiration to all those building design systems.