SHOW ENGINE INNODB STATUS uses different formats to print thread IDs in different sections of the output.
For example, the thread IDs are in decimal in the SEMAPHORES section:
We can see that this semaphore is held by a thread with ID 139857189899008. To find that thread in the TRANSACTIONS section, we have to convert it to hex. This value in hex is 7F330A1F8B00. This conversion allows us to find the relevant transaction:
The main thread ID is also in decimal:
It might be worthwhile to change the output to be more consistent, so that users don't have to do decimal to hex conversions, and vice-versa. If not, then we should at least document this inconsistency.