I had a hard time creating 3D annotation dimensions. They are significantly less functional than in sketches:
- Dimensions always snap to the center point of a radius or circle, rather than snapping to end points, center points, tangentials etc.. So you cannot create e.g. a tangential dimension directly (only a center point dimension). You can, however, define the part (sketch) with this specific dimension, and then derive it from making the sketch visible, deriving the 3D annotation from the existent dimension, and make the sketch invisible again.
So this functionality seems already existant - but not made directly accessible to designers. - Annotation dimensions are always the same type, e.g. a diameter dimension is always (depending on annotation standard) for DIN a one sided arrow to the hole surface, but for ISO a double sided arrow; no idea how to make it horizontal or vertical with projection line... I recall seeing a context menu item "type" for a few dimensions, but it was locked / gray. So to change type of one dimension, I have to change the annotation standard for the complete model (with other settings implied).
Again, the functionality seems to be already existent (in annotation standards), but not directly accessible to the designer on a per feature basis.
