Hi @Anonymous and welcome to the community!
While you are correct that the tool itself does not appear in the hotkey menu, there is a way to make the fly tool into an icon!
I'll walk you through how I did it below:
1. Open the Script Editor and enable 'Echo All Commands' (this allows us to see the code for every action in Maya)
2. Navigate and select the Fly tool so the code will appear in the script editor.
3. Open the shelf editor and create a custom tool and name it Fly Tool
4. Paste the code in the Command tab with the language set to MEL
5. Save the shelf settings and now you should have a button on your custom shelf that will use the fly tool!
Please let me know if this helps solve your issue or if you need any more information!
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