Are your buttons set with "toggle mode" on? I would modify the signals on each button to contain an additional argument which is the name of the button, that way your function knows which button called it.
So each button should have signals like...
on_Squad_Toggled -> in extra arguments: String, "Squad"
on_Squad_Toggled -> in extra arguments: String, "Travel"
... and so on.
Then change your function to something like:
func _on_Squad_Toggled(button_pressed: bool, button: String) -> void:
if button_pressed:
move(Vector2(-720, 0))
# Un-press all other buttons
for M in $UI/Menu.get_children():
if M != button:
M.set_pressed(false)
else:
move(Vector2(720,0))