As mentioned a few times above, I find it helpful to group multiple interests together into clusters: subjects that work well together. It not only makes it easier to make associations between things but it's less stressful thinking of 4–5 "macro" interests than 20 "micro" interests.
For example: Ancient Greek, linguistics, learning science, educational technology, coding are one cluster (and I have http://jktauber.com dedicated to that cluster).
Some interests span multiple clusters. I've already mentioned above how often an interest in education and computational modelling cross cuts interests.
Sometimes that actually helps focus. For example, I've decided a big focus of my interest in wine will be wine education and applying learning science, computational modelling, etc to help teach about wine online (see http://wine.study/ for the result).