I recommend not using aliases as they do not export into subprocesses well. Also, this will fail if you have the explicit interactive shell check on top:
# If shell is not interactive, do not source.
[[ $- != *i* ]] && return
...
Instead make an executable bash script that executes the given instrucions in your PATH.
You can implement this in ~/.local/bin:
#!/bin/bash
MANGOHUD_CONFIG="fps_limit=60,no_display "$@"
Be sure $HOME/.local/bin is included into your path in ~/.profile. Export the variable pls. Use sh syntax, not bash syntax.
Your system information
Please describe your issue in as much detail as possible:
When putting an alias (found in your .bashrc file or similar) as a launch option for a game, it will not launch. Using the entire non-aliased command in the launch options works but this is annoying.
Steps for reproducing this issue