Seriously, Alan Moore did something like this for Big Numbers. Essentially a big spreadsheet on A1 paper. Time across the top, characters down the side. There's an HTML-ized version here: https://stuff.alienbill.com/jamesharvey/bignumbers/
From the description, the novel that was just two people talking sounds like a two-hander play with a single location. Waiting for Godot?
I know it didn't get many comments, but OP, thanks for posting this.
In spite appearances, you are in fact disagreeing with me, because when I use a phrase like "UML Sequence Diagram", I literally mean drawing it on paper with a pencil, scanning it with a flatbed scanner, and then making some minor adjustments in GIMP. I would never think of using a DSL like PlantUML, or something higher level that generates it.
Seriously, Alan Moore did something like this for Big Numbers. Essentially a big spreadsheet on A1 paper. Time across the top, characters down the side. There's an HTML-ized version here: https://stuff.alienbill.com/jamesharvey/bignumbers/
From the description, the novel that was just two people talking sounds like a two-hander play with a single location. Waiting for Godot?
I know it didn't get many comments, but OP, thanks for posting this.