How to display version of Electron environment in an Electron app?

You can, if the App enabled developer tools and enabled nodeIntegration. Take VS Code as an example:

open the Developer Tools, in the console tab, type

process.versions.electron

documentation here: https://electronjs.org/docs/api/process

or try parsing version from userAgent string

navigator.userAgent.match(/Electron\/([\d\.]+\d+)/)[1]