Can we update environment variable through dagster UI?

Not unless you are setting environment variables through the config schema. For example

import os
import json
from dagster import op

@op(config_schema={"env_vars": dict})
def print_env_vars(context):
    # sets environment variables from the config provided
    for k, v in context.op_config["env_vars"].items():
         os.environ[k] = v

    # prints all environment variables
    <http://context.log.info|context.log.info>(json.dumps(os.environ))

So, we just can update through the code right? @Stephen Bailey

in that scenario, you could use the launchpad / ui to update the configuration for each run -- a la

ops:
  print_env_vars:
    config:
      env_vars:
        foo: bar

or

ops:
  print_env_vars:
    config:
      env_vars:
        baz: boom

and that would all be in the launchpad of the UI

I see. I will try it. Thanks so much for your help @Stephen Bailey