About the timer for wait actions

[bonsai]

There are a large number of flows with the "Waiting" status.

All of the waiting parts are "Wait for a duration of time".

Do other flows not operate while waiting with this action?

I think a timer is set for each "Wait for a duration of time" in the flow.

Considering that they are stopped at "Wait for a duration of time", is there a limit to the number of timers that can count up at the same time? ...

[Mark Manders]

A wait condition inside of a flow is just that: it is now 'scheduled' to proceed when the waiting time is over. It doesn't matter how many you have waiting, but it can be messy to find the ones you need, when you need to check on something. 

Also: you can set a flow to trigger 'only if not currently running'. If that's the case, waiting actions can cause an issue (because that flow isn't triggered again on the same record, even if the trigger conditions apply again --> if you have a flow that triggers on 'state = on hold' to wait for 3 days and then do something, it doesn't trigger if it comes from 'on hold' and is later (within that waiting period) set to it again). 

Waiting can be very useful, but it is all depending on the use case and config of the flow(s). When creating flows, always makes sure it can end at some point. Logic like do the following until with waiting conditions that are not set correctly, can keep flows in a waiting state forever if that 'until' is never coming.

[bonsai]

There are about 100,000 waiting flows.
The maximum number of loops is 10, and the wait time is 1 minute for each loop.
Some loops have completed, but some are taking more than 2 hours.
This made me think that there must be a limit to the parallel processing of counting up each flow.

In which module can I see what is being scheduled?
I think if I can identify the record, I may be able to find the cause.

[Mark Manders]

There isn't a limit in in the parallel processing of flows, but they will queue if all resources are used on execution. You need to check on your requirements here. Why do you have these continuous loops? Your issue is not the number of flows that are waiting. Your issue is that they are only waiting for a minute and then start running again. And with 100.000 flows running every minute, you are having considerable performance issues. Especially because your flow is triggered to run again, needs to wait for sufficient resources, then runs and almost immediately needs to run again. 
So no issue with the number of waiting flows. You need to look at why you have configured it with that many runs.