I might be bit dumb to be honest, my brain is still not lined up.
trouble I see is that the tools don't really sit in the spindle cone in exactly the same height from the spindle some tool holders I have might have been reground and they sit slightly in (my guess why they sit different) so I don't have any exact reference point/ height on tool holders from the spindle, one of them being the tool holder for the 3d probe.
One way would be to make a cone to sit the toolholder in and take reference from that cone since they all would sit in that cone the same but different from the actual spindle.
That is why I thought the easiest way would be to touch of the 3d probe on the tool setter but how do I know which input actually triggered the touch? I am not sure if I am explaining my self well.
Here is a quick sketch of what the problem I have is The dimension on the left is not really reliable and that is the main problem I don't understand. It is a cutaway of my exact spindle with toolholder in it.