No this is not possible as the serial data is processed on a polling basis. You can try and slow down polling by setting the optimize setting to “throughput” rather than “latency”:
The Digi was already in the Optimize for Throughput mode.
I switched it to Legacy, then back to Throughput, but I do not see any change in its behavior.
The hoped for outcome would be for the Digi to receive a stream of about 500 characters in a single burst and send that as a single packet over the network instead of 20 character chunks.