UPDATE
I found that the original file's +Joy-Con was a bit different from the -Joy-Con. If the +Joy-Con doesn't fit for you, I would suggest mirroring the -Joy-Con instead of printing the +Joy-Con (the symbols will not match). If I have time, I will get around to fixing this, but for now that is what I have done.

I couldn't get my printer to print the joy-con grips to fit and be easily taken off by simply changing the scales in Cura, so I modified the attachment mechanism slightly. Also, I found that only printing the attachment mechanism saved me a lot of time and filament. So, I've also provided the gCode for my prints and my test prints.

To create the testing gCode, here's what I did: I oriented the model in Cura like normal (see the first photo). Then I set the z-height to -10mm. I used the layer view to find the layer at which the attachment mechanism ended and the actual grip began (see the second photo). Finally, using the post-scripting Cura plug-in, I paused the print at that layer.

*The test for the -Joy-con is the only thing that I've tested so far. I will update as I test more.