IDA has three shortcuts as an alternative to some menus which could be cumbersome to navigate.

Quick view

Probably the most commonly used, it is triggered by the shortcut Ctrl+1 and shows the items under the View > Open subviews menu.

It can be especially useful for opening views which have no dedicated shortcut such as Notepad (although you can always assign a custom one via the Shortcut editor).

Quick debug view

Most useful during a debugging session, this one allows you to bypass navigating to the Debugger > Debugger windows menu by simply pressing Ctrl+2.

Quick plugins view

Last but not least,  Ctrl+3 opens the list of plugin menu items listed under the Edit > Plugins menu, allowing you to quickly invoke a specific plugin. Please note that this list does not necessarily include all installed plugins; some plugins add menu items elsewhere or may not have a menu item at all and work in an automatic fashion.