Using Influxdb node in a subflow - cannot set scope of config node

If I add an MQTT node to a subflow, then in the server setup I select to add a new server, then at the bottom of config node's edit screen I get a dropdown that allows me to select the subflow as the context for the node.

However, if I do the same with Influxdb node from node-red-contrib-influxdb then the db config node does not have that dropdown. That, I believe, prevents me from specifying the database via subflow properties, which requires a separate config node for each instance of the subflow.

Is this caused by something missing from the influxdb node that allows for this feature?

Any thoughts anyone?

I would post an issue on GitHub for the node.

I was hoping someone would suggest what might cause this so I could submit a PR if the fix is simple. Plus it appears, sadly, that the node is no longer supported, judging by the number of unaddressed issues.

I have posted an issue, but I have little hope of anything happening.