To keep track of my novel storyline, I use a flowchart maker called draw.io. It's free online, and you can link it to your Google Drive to have them at hand at all times. Admittedly, it's a bit of work, but it's a godsend to know exactly what you have to write next, so you don't get lost. (Especially when you have multiple storylines, multiple different settings/political situations or things like time travel).
Example: