I don't know a lot about Electron but it seems like you can't do this very well. I guess you can do
electron/electron#1334 (comment) but I can't get it to work. electron-localshortcut also exists but also doesn't seem great. Electron itself only really supports creating global (affects the app even when the user isn't using the app) shortcuts without a menu item.

Given the workarounds above, we believe this module is better implemented in userland (ex. the excellent electron-localshortcut and thus i'm going to label this a wontfix.

electron/electron#1334 (comment)

The other alternative is to get rid of the Shift+Command+Plus shortcut, the menu item will still look "wrong" but at least there will only be one

I'd prefer to find a way to have only one menu item with ⌘+ displayed, while still accepting both Cmd-Plus and Cmd-Shift-Plus, as that's how most other native apps appear to handle this issue.

Looking at Atom, that's what they seem to do, but of course their version is much more complex since they support user remappable shortcuts.

It's a bit sad that this is so hard to solve with Electron... 😓

The other alternative is to get rid of the Shift+Command+Plus shortcut, the menu item will still look "wrong" but at least there will only be one

Maybe that's an okay compromise, since it seems unreasonably hard to do the right thing in Electron.

I don't think anyone ever types Shift-Command-Plus anyway, so at least that would reflect reality.

Use CmdOrCtrl+Plus to make sure that the shortcut icon is displayed correctly