GrumblePuss

This page on Custom Code does a great job giving all the important info about the Json data of a character.

Your idea to write to the reminder of a character seems viable. Perhaps just a collection of keywords in the reminder? Then, each character bio could contain a description + context on what those keywords mean?

Another option could be something similar to the Strict Game Master that uses code to track things like inventory and skills.

Yet another could be leveraging /mem. That is in chronological order (I think) so maybe you can add entries there?

That's... strange. Normally it's the other way around, unless you are doing something unusual, since let has block scope, and var has function scope. Those error normally come from using var as the variable then get's "hoisted" and so becomes visible before the variable is actually declared.

Anyway, good that you were able to figure it out.