To create a symlink to a Google Drive file or document there are a few methods.

You can right click the original file in the Google Drive UI and select Organize and then Add Shortcut

There are also keyboard shortcuts. These shortcuts will change/have changed as of August 1st, 2024. Prior to August 2024 you could select the document you want to symlink, then hit Shift+Z and you'll be presented with a menu to choose the folder you'd like to add a symlink to

After August 2024, the keyboard shortcut is