Manager is basically a web-server written in C#.
Desktop edition just wraps up web-browser + web-server into simple integrated package so it looks like standalone program.
The reason I made it this way is that the same code which runs in desktop edition can be re-used in cloud/server editions. It works very well.
Electron framework works on quite similar principle like Manager. It’s not the same because Electron apps have to be written in Javascript and emphasis is on cross-platform desktop but I imagine if you are careful, you can write Javascript app which can run on top of Electron or as standalone server using Node.js.