Software/App for keeping track of story notes

#1
For the longest time I’ve used notebooks to keep track of my story notes (like plot, character, maps, etc). But i want to venture into the realm of LitRPG writing, and I have very quickly realised that I need some sort of system to keep track of all the skills, classes, power-ups etc.
 
Are there any free software (other than Microsoft Excel lol) you would recommend for this purpose?