[itamarst]

To expand on existing comments, there's two things you need:

1. Relevant technical skills beyond front-end development.

2. Relevant credibility in those additional skills with your current or future employers.

Learning an adjacent technology within your current organization is therefore the easiest way to do this (see https://codewithoutrules.com/2016/04/27/which-technology/). Backend Node.js if you can manage it would be easiest, but backend anything will do.

And yeah, talking to a manager about a change is a good way to learn something new while being paid to do so.

But there are other ways, e.g. years ago I transitioned out web development and into distributed systems by becoming a contributor to an open source networking framework.