In addition, there keep being concepts I tell to several people and I would like to be able to point back to. Especially when there's a key idea that I might miss some pieces of later. So, fine, I guess I'll make an "ideas" category and put some things in it.
To try to stay on theme a little more, I'll note how formulating an idea can be a process a lot like building something, for me. It likely starts with a sense of what I want the end to be, but no clear plan for how to get there. Or, it can start with some raw materials that I want to combine well. I can let the raw materials, whether they are the focus or not, spin around in my head for a while, and I often seem to expect that I'll be able to come up with a complete image just with the power of my mind.
Often, this isn't true. There are too many variables and possibilities, often with no clear way to choose among them. They can be equally good, or hard to evaluate. I benefit a lot from getting started in some way that narrows things down. For projects, this often means taking the first few parts and picking a configuration to put them together. Either it works and now I have a real starting place, or it doesn't and I learn from that. For an idea, the key is getting out of my head and applying language, which might mean writing it out, or might mean telling someone. For writing, I have to overcome the tendency to skip over what I "know," because if I do then I'm back where I started, stuck. Better to write the obvious parts, as has to happen when I frame an idea in a conversation, and then I can start to progress. It works surprisingly well.