Consider the support of variables and variable environments in Fiddler Everywhere. The base functionality should have:

- Option to create a static variable

- Option to create a dynamic variable (e.g., one populated dynamically from response).

- Options to use variables in Composer, Rules, and Inspectors (e.g. for dynamic population)

- Option to easily access and modify stored variables.

- Option to store variables in different environments (e.g. stage, production, etc.)

- Option to share variables/environments.

+2 Requested from 1640564 and 1640556