Oh, there are hundreds that I've started categorizing them. They outgrew the storage capacity of my head / brain. I've tried a lot of productivity tools to organize them, but in the end, all my project ideas just remain ideas scattered somewhere unless I see it action and go like, "Hey, I had that same idea. I wonder when they got the idea. Was it before or after I had it?" In the end, I just console myself saying that for me it was only an idea in my head when those people saw it through execution and has a working product. The next step for me is to get along with them and collaborate and make that idea better rather than re-invent the same wheel again according to my idea.

Nextcloud is the biggest example of an idea that came to me and remained in my head and is still on a todo list somewhere.