Dear Friend,
You can
Add the files as a link to the file to one of your projects.
Use Add an Existing Item to the project you want to add the file to - the Open button has a small down arrow, if you click that you can select Add as Link.
This will add the file as a link from the original location, meaning you only have one physical file.
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Please don't forget to mark this as your answer if it helps you out.
Regards
Varun Sareen