Q:

IntelliJ IDEA does not expand environment variables in Program arguments in Run Configuration

Same in Using environment variables in “VM options” and “Program arguments”, the environment variables cannot be used in Program arguments in the Run configuration.  If I put $VARIABLE in the Program arguments (VARIABLE is configured in Environment variables in the Run configurations.  
None works. 

$VARIABLE
${VARIABLE}
$VARAIBLE$

Is this a bug? 
Environment
$ cat /etc/os-release 
NAME="Ubuntu"
VERSION="18.04.2 LTS (Bionic Beaver)"
ID=ubuntu

A:

It's a bug affecting user environment variables defined in the same configuration, it works for the system environment variables.