I still cannot see my custom parameters in Firebase Analytics, but I have found out how to use BigQuery to see the data I want.
It explains how to do queries that access your custom parameters and values.
In my app, I defined special events so I would know which levels are easy, hard, and very hard. An easy level is one that a player beats in one or two tries; hard, 3-4 tries. After watching the video, I figured out how to use UNNEST to get to the custom parameters.
Here is an example of a query where I get the counts by level for the number of users who found specific levels easy. The custom event is named "h_easy_level" and the level value for those events is named "h_level".
SELECT
param.value.int_value AS Level,
count (*) AS NumUsers
FROM (
SELECT
*
FROM
`analytics_253349235.events_2021*`
WHERE
(event_date > "20210309")
AND (geo.city != "Raleigh") ),
UNNEST (event_params) AS param
WHERE
(event_name = "h_easy_level")
AND (param.key = "h_level")
AND (param.value.int_value <= 40)
GROUP BY
level
ORDER BY
level;
Yes, it is a bit complicated. You are seeing the end result. I'd suggest working on small problems first and then combining what you know. For example, I started with a query for multiple days of events. I added onto that what I learned from using UNNEST for custom parameters.
The multiple days part is this:
FROM
`analytics_253349235.events_2021*`
WHERE
(event_date > "20210309")
So I have one way to look at analytics data for my game. I hope this helps others who are trying to understand their apps.