You can run the game on a seperate screen. Process:

Once you press "Play Game" when you first open the window, you should be able to see the fullscreen button on the bottom right. 

Inspect Element the fullscreen button.

Immediately, it highlights a something along the lines of: "<img src=*link*...>

Navigate 2 lines below that and you'll see another line of code that starts with: "<iframe frameborder...>"

In the code mentioned above, there'll be a link that ends with a url of "index.html"

Open this link in a new tab and you should have the game run

The browser will ask for permission on being able to use clipboard in this tab, just agree to it.

You can now copy and paste your save files

An example of a save using this method:

7b224469617279456e7472696573223a7b22756e6c6f636b65645f64696172795f656e7472696573223a5b2264696172795f656e7472795f74657374222c2264696172795f656e7472795f66616369616c5f73686f776e222c22616e6e615f736578222c22736f6e735f667269656e645f7365785f6f7665726865617264222c22736f6e5f63686173746974795f31222c22736f6e735f667269656e645f7365785f77617463686564225d7d2c2247616d655374617465223a7b22646179223a32302c2264617974696d65223a224576656e696e67222c22696e74726f5f68617070656e6564223a747275652c226e6578745f636f73745f647565223a327d2c224e616d6573223a7b22436f6c6c6567654e6572644e616d65223a225374657665222c2247796d42756464794e616d65223a22416e6e61222c224d6f6d4e616d65223a224d6f6d6d79222c22536f6e4e616d65223a22436861726c79222c22536f6e73467269656e644e616d65223a224d617263227d2c2250726f6772657373223a7b226368617261637465725f70726f6772657373223a7b22626f7373223a362c22636f6c6c6567655f6e657264223a332c2267796d5f6275646479223a372c226f665f63686174223a302c2272616e646f6d5f73747564656e74223a372c22736f6e223a302c22736f6e735f667269656e64223a357d2c22756e6c6f636b6564223a5b226f75746669745f73706f727473222c22736f6e5f63727573685f31222c22736f6e5f63727573685f315f68617070656e6564222c22746f795f6d616769635f6d6f616e5f77616e64222c226f665f6f70706f7274756e697479222c22736d61727470686f6e65222c226f6e6c796661705f617070222c22626f64795f7061696e74222c2263686173746974795f63616765222c226f75746669745f756e64657277656172222c224f465f756e64657277656172222c226f75746669745f6e756465222c22736f6e5f63727573685f325f68617070656e6564222c224f465f6e756465222c226f75746669745f62696b696e69222c22736f6e5f6375636b65645f315f68617070656e6564222c2273657873686f705f72656e746564222c2273657873686f705f707269766174655f726f6f6d222c2273657873686f705f706f6c65222c2277656263616d222c2273657873686f705f61647665727469736564222c2273657873686f705f616476657274697365645f736f6e5f7365656e222c226f75746669745f6c696e6765726965222c2266657274696c6974795f64727567222c22626c696e64666f6c6465645f6c69766573747265616d5f68617070656e6564222c2262757474706c7567222c226f6e61686f6c65222c226f6e61686f6c655f676976656e222c22736f6e5f6375636b65645f31225d7d2c2253617665466f726d617456657273696f6e223a2231222c225374617473223a7b22636f7272757074696f6e223a38372c22646563656e6379223a35352c22656e65726779223a352c2266616369616c5f616374697665223a66616c73652c226d6f6e6579223a3334332c226d6f726e696e675f6f7574666974223a226461696c795f64656661756c74222c226f7574666974223a226461696c795f64656661756c74227d7d