First up, I think you a referring to the Writer when you say you click on the three dots.
When reading the map from the bike, the Reader will save it to the folder you selected with the browser window. It's not placed randomly. When you click the 'Read' button, it defaults to the folder that the Reader is being run from. I suggest creating a 'GuzziDiag' folder, and put GuzziDiag, Reader & Writer in there. When you save the map from your bike and the browser window opens, type the name you want to call it, and click 'Save'. It will save it in the same 'GuzziDiag' folder. Now, when you run the Writer, if the map is in the same folder, it will appear in the browser window without having to search for it. The Writer program will only see maps of the correct type for your bike, so make sure you are using the correct version. In your case, the IAWMIUG3Writer.
You haven't said what map you are writing. Are you just going to write your saved map as a test, or do you have a new map?