Pictures should suffice for the curious.
The new format is simply a 7zip file with stuff inside. You can add stuff and edit stuff and make distributing your toolbox easy. There are json-ish files and text files inside the zip format.
Have a look.
5. Open any of the files in your default text editor.
6. Select a file
7. Choose Edit
8. Fix minor edits without having to fire up Pro.
Play with a scrap toolbox or a copy your working toolbox.
I develop all my tools in the 'custom toolbox' since it provides the best environment for documentation (eg. screen grabs of tool parameters etc)
Editing, including other information and data is easier since it is zip archive.
Have some fun.