Download a newer version of nw.js (eg. v0.54 or an older one) and extract the files into a new folder (right windows). On the left side you have the original game files (in this example I downloaded the compressed version). Compare the engine files with the game files and copy the game assets files and paste them into the engine files. Here you have to paste the "www" and "package.json" files (see marked files on the left) into the newer version of nw.js (right window). That's all.
The same you will have to do for the other game. Create a copy of your engine folder (right folder) and paste the other game's "www" and "package.json" files into it. Done.
Sometimes you have do use an older version of nw.js, because the newer ones are buggy. You can get all previous versions from here
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. Start from v0.52 and then go to the next higher version (v0.52.1/2 or v0.53).
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