Pressing VO+H, with VO being either Control+Option or CapsLock depending on your configuration, will bring up the VoiceOver help menu, which contains a hierarchical list of all the available commands with their currently assigned key bindings, and pressing VO+K will allow you to press any key combination to hear a description of whatever action is currently assigned to it in VoiceOver. The remaining application-specific key bindings that are totally independent of VoiceOver are all enumerated on their respective menubar menus, so just browsing those will allow you to learn what's available. Most VoiceOver key bindings, keypad actions, and trackpad gestures can be customized in the latest major versions of macOS, and some applications also allow you to customize the key bindings that activate their specific menubar menus.
Comments
Isn't it already available?
I believe there is one already done by AppleVis member. So check Getting Started with your First Mac and see.
Just press VO+H
Pressing VO+H, with VO being either Control+Option or CapsLock depending on your configuration, will bring up the VoiceOver help menu, which contains a hierarchical list of all the available commands with their currently assigned key bindings, and pressing VO+K will allow you to press any key combination to hear a description of whatever action is currently assigned to it in VoiceOver. The remaining application-specific key bindings that are totally independent of VoiceOver are all enumerated on their respective menubar menus, so just browsing those will allow you to learn what's available. Most VoiceOver key bindings, keypad actions, and trackpad gestures can be customized in the latest major versions of macOS, and some applications also allow you to customize the key bindings that activate their specific menubar menus.