Hey!
I believe there is a way to do that and it should be fairly straightforward.
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Open IWM in the same browser you have been using to play the web version.
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In the upper-left corner, you should see a very light grey button with three horizontal lines.
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Click on it, and you should find an option called Export Saves. Selecting that will download your save files.
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Download the executable version of the game and open its files. You should find a folder named saves.
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Place the save files you exported from the web version into that folder.
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Start the game afterward, and your saves should appear there.
I hope I managed to explain that understandably, haha.
Warm regards!