@Will introduced me to the idea of using signifiers in the titles of one's notes as a way to quickly see something (like a structure note) without having to search for it. I quickly adopted this idea and have ended up creating several signifiers, leading me today to create a legend for such things. I'll add that to make the signifiers stand out to me, I used Greek letters. Being a humanist scholar, I know enough Greek for this to be useful. Other users likely prefer other symbols.
What signifiers do you use?