This is what I mean:

Thanks!

Something like this should work (pseudo code):

class MyTool(EditingTool):

    def getMarqueRect(self, offset=None, previousRect=False):
        if self.myToolSelection:
            return None
        return super(self, MyTool).getMarqueRect(offset, previousRect)

def canSelectWithMarque(self):
    return False

see the polygonSelectionTool as example.

(side note: I don't know why this is not is added to the docs, will investigate)

Any idea why this is happening?

You can overwrite:

def dragSelection(self, point, delta):
     if myToolHasMySelection:
          # do you own dragging
     else:
         super().dragSelection(point, delta)

from mojo.events import EditingTool

help(EditingTool)