Using a string value (multistate) as Y-Axis

[LeeDr (Lee Drengenberg)]

Here's 2 things you could try;

1). The Advanced JSON Input you mentioned. I do have this example where each doc had a start time and a duration in sections and the user wanted the chart to the totals of everything active at any particular time. So this user could pad the data based on information in each document. Your case is different in that each doc changes a state and doesn't have any information on when the next state change happens. But here's the example;

Display concurrency in data on Kibana

I have fields with start date and duration (seconds) representing start and duration of a phone call. I would like to define concurrency (a number) when the same destination (also a field) is active within the same duration. That is if a ncall starts now for 30 seconds and another call to the same destination starts 15 seconds into the first call, concurrency should be 2 for the remaining 15 seconds. How do I define this in Kibana visualization as a line graph over time?

2). Have you tried Timelion? It was a plugin but is now built in to Kibana. It has a derivative function that might work with your change of state type data.
Check out; Timelion: The time series composer for Kibana | Elastic Blog
And; Timelion | Kibana Guide [8.11] | Elastic

Regards,
Lee