Look at chapters 37-40 in the IMXRT reference manual, and if you have not already downloaded it, you can from the PJRC webpage:
https://www.pjrc.com/store/teensy41.html#tech
Thanks for the response, I appreciate it. Sometimes what is obvious to some is magic to others.
Even at 75 I am still learning daily!
For example, some of the pins are for the: Medium Quality Sound (MQS) and the signals are described in chapter 39
There are also some that are SPDIF chapter 40
And the others are SAI pins (chapter 38)
Another page from my excel:
View attachment 29799
Note they are marked in blue on this page