How can I start my network with the companies I work for?

TLDR: Fair worker needs to change his current working relationship, he would like to become a freelancer and use his current working relationship with his boss and his client to build his network. How to put the question to both? How to manage them without generating problems for either of them?

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Good morning, I’m a developer since 2009, I started working with .NET applications and today after 11 years I’m currently a developer of "Custom functions" for an IBM tool for a bank (some sort of Back-end developer with limited power). I’m a fast learner, jumping from technology to technology, I’ve always learned while working in the first week and then be autonomous after. I’ve always been "the wild card up their sleeve" to my employers.

I’ve been working in a small consulting company for 6 years now, with 10 developers top (never seen more). I have almost always felt comfortable in this company, but in the last two years I feel neglected (last year they did a React and POS interaction course at the company and I was not included), not taken seriously and underpaid.

In my current job at the client I am the only developer, a great position for many, the only person to assign development tasks in a group of 4-5 projects. Sometimes the situation is very boring for a short time and sometimes it is very stressful over long periods of time especially when my priorities are not handled correctly and deadlines crossed.

This situation and this stalemate exist for two years now, I have been asking my company to find a new job for me, I would no longer want to deal with the IBM product, at least not 8 to 17. In these two years I have been called twice for job interviews for unclear projects, only to discover that I am not the right fit. I also tried to ask them to find a solution with the client so that I could work from company headquarters, but they never tried to contact the client.

Tired of the situation, at the beginning of the year I started my self-training as a Web Developer (the pandemic helped), I dusted off my HTML, CSS, javascript and got up to speed with React, Node, being active on Git and the new ECMA features. I’m currently building my portfolio and I’m thinking about what to do with my future, setting the end of the year as the limit to do something.

What I wanted to ask you is some advice on what to do in my current position. I would like to change my relationship with my company, leave my current client (at least as it is, I would like to turn it into an "on-call" contract, so that I can deliver what they require with certain specifications and then not see them for X time). I’m attracted to the idea of becoming a freelancer, but it’s foolish to leave a safe job before building a network and if someone has advice or resources on how to do it properly I’d be grateful. Can I start building a network with the companies I work with? How could I introduce the idea to the client for this kind of change? What about my current employer? Because I understand the unethicality of stealing a client.

Thanks for your time