I have been building a new project on my RPi for almost 9 months. It is my first RPi project. I think it is "ready for prime time". My problem is, the existing SD card is full of trash. During my attempts to understand and use the RPi I know I did many stupid things installing, uninstalling, etc. I don't know what programs and utilities I actually need. I would like to make what I created open source so I need to know what is actually needed. And only what is actually needed.
I'm thinking I start with NOOBS, OpenHABian, mosquitto, and rtl_sdr, all of which I know I need. I also have a C program I wrote...my first C program ... that I need. My OpenHAB setup also has many items, rules, sitemaps, etc that I created. Many of which I no longer need. But I don't know which I need and which I don't.
Something tells me the ideal way to do this is running 2 RPis. One with the existing SD card and a new one starting with the bare bones installations. Then run the new one, see what fails, go to the existing one and find what I need. But I have only one RPi. Is there a way I can use my windows desktop to access the existing SD plugged into the desktop? Just to see what is on it and copy what is needed to the RPi. Or plug the existing SD card into a spare USB slot on the RPi?
Or are these all really dumb ideas and there is a simpler way?