For many "one-person teams", finding an easy way to manage tasks, projects, and ideas can be difficult, and it seems like every tool out there has a limitation, leaving many people to rely on Apple Notes or Pen and Paper. What issues have you seemed to face in this regard?
I heavy relied on editing wiki pages (on a self-hosted Mediawiki instance) in the past. It can work, but it gets really tedious. These days I use a Bugzilla instance. Actually, I use two Bugzilla instances: one that's public, for opening issues against our Open Source projects, and a separate, private instance, that holds a lot of items that aren't necessarily "bugs" but are just "tasks" that need to be done. It does also hold bugs, either security related bugs that we don't want to make public, and/or bugs against our internal infrastructure and tooling.
That, along with continuing to use Mediawiki for documentation and what-not, works out reasonably well for me.
That, along with continuing to use Mediawiki for documentation and what-not, works out reasonably well for me.