I have been writing down my thoughts for several years now, testing many types of note-taking and switch between different softwares. Right now I use Obsidian to do all of my note-taking and thought organizing. As the header staes, I have named this collection of text and images, a Signspace. The name might change in time but the concept is core to how I format my "second brain".
Define Signspace
a system of signs that is used to express and document ideas, definitions, and complex thoughts