Subscribe to this MOD, you will modify this MOD instead of doing a new one, you don't need to create any folder, you don't need to create any file, you will change the value inside this MOD's files.

After subscribing and downloading the MOD, go to where you download it, the default directory is this one:
...\steamapps\workshop\content\211820\729524482
Note that "211820" is Starbound's ID on Steam and "729524482" is the MOD's ID on Workshop.

Now you will see a zip (probably) file called "content" and you can't opening it because it's a ".pak", download any text reader as Notepad ++ and open using the text reader.

Inside this mess (I know you can't understand what are you seeing) you will open the search (Ctrl F on Windows) bar to search a word, you will search for "160". Once searched you will see this:

"op": "replace",
"path": "/bringAdjacentWindowGap",
"value": 160

Change the value of to 420 or whatever you want to change, this value is the number of pixels between windows. Important to say this the pixels between the right corner of the inventory and the left corner of the window you just opened inside the game, which means if the window is too big and you insert a too high value, the window can be drag out of your screen.

I'm using 420 but at the point, I'm doing this tutorial I didn't test all good looking values yet, so 450 could be better, or 500, I don't know. This is how 420 looks like:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1987831154

If you are wondering why do I have 40 pixels, it's because I'm closing and opening the game all the time to test values, it seems it saves those 20 pixels inside the storage every time you collect it.