Electron で Mac 版のバイナリをビルドすると、標準ではショートカットキーが効かなくなるようです。以下の JavaScript を差し込むことにより、ショートカットが効くようになりコピー&ペーストなどが行えるようになります。
var Menu = require("menu"); // Create the Application's main menu var template = [{ label: "Application", submenu: [ { label: "About Application", selector: "orderFrontStandardAboutPanel:" }, { type: "separator" }, { label: "Quit", accelerator: "Command+Q", click: function() { app.quit(); }} ]}, { label: "Edit", submenu: [ { label: "Undo", accelerator: "CmdOrCtrl+Z", selector: "undo:" }, { label: "Redo", accelerator: "Shift+CmdOrCtrl+Z", selector: "redo:" }, { type: "separator" }, { label: "Cut", accelerator: "CmdOrCtrl+X", selector: "cut:" }, { label: "Copy", accelerator: "CmdOrCtrl+C", selector: "copy:" }, { label: "Paste", accelerator: "CmdOrCtrl+V", selector: "paste:" }, { label: "Select All", accelerator: "CmdOrCtrl+A", selector: "selectAll:" } ]} ]; Menu.setApplicationMenu(Menu.buildFromTemplate(template));