Reworked handle selection. Now you can only select one by default, and deselect with clicking far away from handles (when nothing is held down). Holding down shift will always append, and holding down control deselects one by one.

game/addons/mesh_data_resource_editor/MIDGizmo.gd

@@ -217,18 +217,36 @@ func forward_spatial_gui_input(index, camera, event):
 						closest_idx = i
 
 				if (closest_idx >= 0):
-					for si in _selected_points:
-						if si == closest_idx:
+					for si in range(_selected_points.size()):
+						
+						if _selected_points[si] == closest_idx:
+							if event.control:
+								_selected_points.remove(si)
+								return true
+								
 							return false
 					
+					if event.control:
+						return false
+					
+					if event.shift:
+						_selected_points.append(closest_idx)
+					else:
+						# Select new point only
+						_selected_points.resize(0)
 						_selected_points.append(closest_idx)
 
 					apply()
 					redraw()
 				else:
+					# Don't unselect all if either control or shift is held down
+					if event.shift || event.control:
+						return false
+					
 					if _selected_points.size() == 0:
 						return false
 					
+					#Unselect all
 					_selected_points.resize(0)
 
 					redraw()