This app was mentioned in 16 comments, with an average of 1.38 upvotes
I'm not sure if this is what you're talking about but there's Mindly
Basically a note-taking app but with different circles, kind of like dendrites. I use the app a lot.
Made a reply to the top comment, but I'm going to reply here too, so you get the notification, OP.
Check out Mindly. It's a great mind mapping app. It's simple in its design and just flows. My design process always uses mind maps and Mindly is the best app I've ever used.
I'm going to latch onto this comment to plug Mindly. It is a mind mapping tool that I use for literally all my design documents.
Basically my process is the same: I conceptualize (basically the elevator pitch), then I abstract the game (by making headers in Mindly), then I begin to define my abstractions (by building sub headers and linking them/fleshing them out).
When I do this with Mindly, the end result is a very detailed map of my game and all its elements. I can look at it and navigate it in real space. I'm also ADHD and being able to physically interact with ideas is almost entirely necessary for my design process. The best part is that Mindly creates a PDF version of your map for you that is nearly formatted and can be used as a traditional design document.
I used an app called mindly https://play.google.com/store/apps/details?id=com.dripgrind.mindly
I would suggest this https://play.google.com/store/apps/details?id=com.dripgrind.mindly&hl=en
Mindly (mind mapping) // video
TheBrain: Not really circles but visually items reorganize around subtopics when you drag them - currently has problems in Android Pie.
I use this mind mapping app to get down ideas when I have them.
https://play.google.com/store/apps/details?id=com.dripgrind.mindly