I am using Apache NIFI, how I can change/modify/replace value of global/environment variables?
You can change the variables with REST API, but I wouldn't suggest this.
1. In this case within NIFI Cluster version numbers could be different between Nodes
2. After variable update a restart is required for controller and processor too (it doesn't matter if you changing it with REST API, or with other methods), you can check the process, when you manually changing it.
It's better to create a flowfile with attributes, or write-back data to sources (if it's a database), and compare it from there if possible.
If you have an another solution, please share it :).