Menu action for "midi learn" (ctrl+middle click)?

  1. Is there a menu-action (action-name) for midi learn function that can be used in scripts/midimaps etc?
  2. Can user change default ctrl+middle mouse button to something different (preferably just middle mouse button or some additional mouse buttons)?

No, neither of those is available at this time. In the case of 1, the user has to have physical access to both the GUI and the control surface at the same time, they have to be close together. So being able to set learn from the surface doesn’t add much. For 2, perhaps add a feature request at https://tracker.ardour.org/ or at least wait for Ardour 6 where the menu action code is being reworked.