In Google Drive it is possible to 'add selected items to an additional folder'. This means that you can have a file in more than one folder. You are not duplicating the file - you are just putting access to it in more than one place.
- Select the file you would like to have in more than one folder.
- Move the file to one of the folders you want to keep it in. Do this by 'right-clicking' on the file and then choosing 'Move to'. You then need to choose the desired folder.
- Then click the folder to which you would like to add the file. You are not copying the file. You are just adding access to the file to an additional folder.
Other keyboard shortcuts for Google Drive on the web can be found here.