You might be interested in chronos' future tracking feature: https://github.com/status-im/nim-chronos/blob/master/chronos/config.nim#L31
The way we use it is to expose it via a REST interface so that all in-flight tasks can be tracked:
https://github.com/status-im/nimbus-eth2/blob/unstable/beacon_chain/rpc/rest_nimbus_api.nim#L254
I'm not aware of any equivalent in asyncdispatch, but then again, we don't use it so others might know more.
Sorry for the late reply.
It seems that asyncdispatch does not have the ability to track status. I will take a look at the internal implementation of chronos you mentioned.
However, I'm currently using nmqtt etc. and cannot switch to chronos right away.