File Picker
When selecting files in CodeGlass (for example, a Project.toml file), you will see a button next to the input field. Pressing this button sends a message to the Engine to open a file picker.
The reason CodeGlass opens the file picker from the Engine is that the Client cannot access the full path of a file, while the Engine needs the full path. This approach does, however, come with some limitations.
The file picker opens on the computer where the Engine is running. This means that when using a remote connection, you cannot use the file picker.
MacOS
On macOS, CodeGlass uses osascript to open the file picker, so there should be no issues here.
Linux
Because Linux does not have a standard file picker, CodeGlass uses the XDG Desktop Portal to open one. This is not supported by every distribution, but you can check which distributions support it here.
Windows
Because the Engine has no UI, the file picker will most likely open in the background. When the message indicating that the file picker is open is displayed, you will need to press Alt+Tab to switch to the file picker.