Environment variables helped to solve creating a custom config table in the environment. The beauty about it is, it can be packaged as part of the solution and move form one environment to another without any manual transportation.
Initially when it was introduced, we need to do multiple queries looping to get the default or current value of the Environment Variable in Power Automate Flow. This is a hassle to use when we already had multiple steps in your flow. Then there is a FetchXML option to query it and it also occupies one or more steps to retrieve the value of the Environment Variable.
To answer to the problem, now the Environment Variable are available as a Dynamic Content value. You can able to add the Environment Variable value with out any listing or fetching. This is so simple as adding the value using variable. Point to note is it will list the current value, if you need the default value then remove the current value and it will return the default value instead.

Awareness is the greatest agent for change
Eckhart Tolle