I don’t have ADHD, but my trick for introducing these chain-of-thought topics back into conversation is like this:
One degrees of separation: normal topic, can be added to conversation with no introduction
Two degrees of separation: “You mentioned ______, which made me think of _______”
More than two degrees of separation: Either don’t bother, or, if it’s really interesting, then wait for a good time and then hit 'em with "Hey guys, sorry to interrupt, this is kind of random but I just thought of… "
I don’t have ADHD, but my trick for introducing these chain-of-thought topics back into conversation is like this:
Works pretty well most of the time.