App shortcut (custom by private)

Hi there

I tried to put in App Short customed by me, But it's not working at all weirdly if I put function key on other shortcuts (such as Show notification center ) It super work well

How Can I open the Email app just by pressing the f1 key? (already set as standard function key)

You are using that feature totally wrong! The menu command is not the top level menu name, its what's under the top level menu name that are commands Please have a look at: Create keyboard shortcuts for apps on Mac

That said, this is not even the right place to create a keyboard shortcut that opens an application. As an example, you can create a Quick Action/Service in Automator and open an application, then assign it a keyboard shortcut in System Preferences > Keyboard > Shortcuts > Services, not: ... App Shortcuts

There are several third-party application that keyboard shortcuts can be assigned to programmed actions and any one of them may be better than using an Automator Quick Action/Service. For example I use FastScripts and Hammerspoon to assign keyboard shortcuts that in turn when pressed run AppleScript scripts, shell scripts, Lua code, etc. to accomplish all sorts of tasks. For example, in FastScripts I press F6 to empty the Trash without prompting. This is because the F6 key is not assigned to anything else on my system, so with nothing to conflict with it, it just works.

FWIW Using a single key as a keyboard shortcut can be problematic and generally speaking (IMO) should not be done. Also, depending on other system preferences pressing the fn key may also be necessary, as by default pressing F1 adjusts the brightness of the screen.

If you keep the Mail icon in the Dock you can a open it with a single-click vs. a single-keypress.

As previously mentioned about other system preferences, in e.g. macOS Catalina in System Preferences > Keyboard one must check the [√] Use F1, F2, etc. keys as standard function keys checkbox to use the function keys as standard function keys and with that checked and with the following snippet of Lua code in Hammerspoon it opens Mail, or if its already open it focuses it. Otherwise I'd also have to press fn with F1:

hs.hotkey.bind({}, "f1", function()
    hs.application.launchOrFocus("Mail") 
end)

_{Note: I am not affiliated with the developers of the aforementioned third-party applications, just a satisfied user of the products.}