short answer. The Modbus nodes dont support that.
There is a recent discussion here regarding using environment variables but thats not truly dynamic configuration since (from what i understand) env variables update on system restart?
you could open a feature request on the developer's Github page
may i ask why you want to do this and how many modbus devices do you have?
the best solution now is to create multiple modbus-client nodes and Flex-getters
the only use i cant think of is trying to dynamically loop through an array of ips and connect to a list of modbus devices.
