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.
