Hi Martin, yes that would make sense for extrude to point to take a distance, unless "Unlock direction" is picked. That would definitely be something I can add for v4.

In the meantime, you can get a particular distance by clicking "Unlock direction", then typing in your desired distance and hit enter, which will trigger a distance constraint, then drag out a construction line, the end of the construction line will be at that distance and you will have a snap point there to snap onto.

- Michael