(Spent way too much time in UTM's Drives → New… and mucking about in config.plist before this brain-wave):
Create a new blank image in Disk Utility (Cmd+N)
Set filename, size, format, etc. as desired
Select the VM in UTM's sidebar → click the "Edit selected VM" button in the toolbar
Under "Drives" click New… → check "Removable" → click "Create" then "Save" to close the settings window
In the VM's main pane, scroll down to the "External Drive" dropdown menu (which has now appeared) → select Browse… → double click the DMG file created in step 2
/mac | Sep 07, 2024