How I Keep Track of What's Happening in a Complicated Plot

I'm currently reading the Primal Hunter 3, and one problem I've run across, which I've dealt with in previous reads, is this:  I can't keep track of what's happening.  There are a lot of characters and plot lines to keep tabs on.  We have our main character Jake, who is kind of a loner and does his own thing.  There's Jake's brother, and Jake's best friend slash Primordial god Villy, who has his own thing going.  Then there's all the sub characters who I'm not going to even bother writing down here because I can't.  

I've devised this tool to help myself keep track of everything.  Mind you, this is the first one I've done, so I'm not fully utilizing it to full potential.  What I've done here is written a brief one to two sentences for each chapter.  This is a place where I can summarize what I remember from that chapter and thought of as most important to keep track of for later.  So far, I've mainly used this to track what Jake, the main character, is doing.  He's so busy.  In the future though, when I use this strategy for other similar books, I think I will put in character tabs underneath the chapters.  For example, under Chapter 25 I might put Meira in a different color and follow up with a summary of what I need to know about her plot line at that moment.  

Obviously, everyone's minds work differently, but the way mine works, I tend to discard information unless I can prove to my brain that the info is important.  So when an author introduces a new character, such as Meira the puny human, my brain just says, Okay... Why is this here.  Who is this person?  Why do I care?  Why should I care?  I'm literally so not interested in whatever this is." TRASH!  It's unfortunate.   So the solution for me is to write whatever it is down.  Defeat the brain.

 

What are you tricks for keeping track of those complicated plots?  Curious.