ENGDOCS-1716 (#18385)

* ENGDOCS-1716

* tweak

content/compose/environment-variables/envvars.md

@@ -21,6 +21,7 @@ This page contains information on how you can set or change the following pre-de
 - `COMPOSE_PATH_SEPARATOR`
 - `COMPOSE_ANSI`
 - `COMPOSE_STATUS_STDOUT`
+- `COMPOSE_ENV_FILES`
 
 Compose also inherits common Docker CLI environment variables, such as `DOCKER_HOST` and `DOCKER_CONTEXT`. See [Docker CLI environment variable reference](/engine/reference/commandline/cli/#environment-variables) for details.
 
@@ -141,6 +142,12 @@ The default value is false to clearly separate the output streams between Compos
   * `false` or `0`, to disable.
 * Defaults to: `0`.
 
+### COMPOSE\_ENV\_FILES
+
+Lets you specify which environment files Compose should use if `--env-file` isn't used.
+
+When using multiple environment files, use a comma as a separator. 
+
 ## Unsupported in Compose V2
 
 The environment variables listed below have no effect in Compose V2.