Just display the hole sketch and you can put your side on it and if it doesn't work I cheat by putting a circular sketch in the center of the hole and the side at the right diam.
For your drawing and the dimension of this hole, you have to make a view according to the inclination of the hole and normally your dimension should appear.
And so this view of the can do it in the 3d or MEP...
Thank you very much for your answers, which indeed seem to be the right solution.
I also confirm that by tilting the model (Insert / Functions / Move & Copy then rotate) at the precise angle of the cone, I can then dimension the inclined hole in the MEP. However, this impacts all views because the tilt is applied to the entire model.
So my last problem is to be able to create an angled view exactly at the angle of my cone, which I can't do. (Yes sorry I'm starting with Solidworks :-)
If you could guide me on this last operation, it would be very nice!