I am having some difficulty in parsing out the situation you are trying to achieve.

If you're thinking "software studio" like "art studio" or "PR firm" or maybe a "legal practice" ? That sort of thing doesn't really exist yet (it may but it probably won't for another decade at least) but not to rain on your dreams let me share a bit how I reason to that;

Given the current working environment, there a few kinds of software "situations"[1] and each have their plusses and minuses.

The simplest is "employee" (which I know you're trying to get out of) but there is a reason that companies maintain a stable of employees whose only job it is is to create software. It is an economical way to spread the cost over a variety of software needs, especially for vertically integrated companies.

The next simplest is the software contractor. The client tells you what they need, maybe puts some parameters around it and gives you an unreasonable deadline[2]. The upside is you can pop these off and generally they will pay the rent. If you're specialized in a particular thing they can even pay more than the rent. The freedom to come and go as you please it a plus, that you need to line up the next one before the current one ends, kind of a pain. Evaluations are also often more stringent as the clients are typically paying you more per hour than they pay regular employees so they darn well get their money's worth.

A more complex one is developing a boutique software product and focusing on that. I have a good friend that developed all the software for some industrial control systems and they can just sell it again and again to people who are setting up factories or other control processes. I think the typical way these form is someone is contracting and starts reselling the software they wrote on one job to others. (note you need to include language in your engagement contract to do this!) But there are a lot of industries where they need an "out of the box" solution. One person I know did this for their local church and then resold the same package to half a dozen of the churches in town.

The important thing to understand is that software is worthless. I can be fun to write (I enjoy it tremendously and write software for fun) but to be economical it has to serve a purpose for someone who is generating some sort of economic product. And writing any software product has parts of the software that is boring/lame to write and that part of a project will always feel like a job.

There is however one way to write software for fun without having to deal with deadlines and impatient bosses, and that is to get a job teaching programming somewhere. You can write things and go over it with your students, you can see how they write things and help them get better at it. You do have to deal with "school politics" which is a thing but the software you right doesn't have to "do" anything, just be illustrative.

So if you had hired me as a coach and posed this question, the first thing we'd do is put yourself in your "software studio" and write down what your day to day looks like, who your customers are, and why they are paying you as opposed to hiring some contractor or a full time employee (FTE) to produce the software they need. Then work backwards from there to the present to get a handle on what milestones you might expect between your current situation and that one.

[1] I'm going to leave off the one where you work as an employee of a company that is growing and gives you stock options so that after some number of years you can pay yourself from gains on your investment portfolio and spend time writing what ever code you want. Perhaps surprisingly a lot of people fail at this (they have the means but just making up things to do is not one of the skills)

[2] I'm not sure why but of all the software contracts I've taken on over they years I have yet to have someone say, "Take as long as you need to get it right, that is so much better than getting it fast." :-)