Will you be able to limit the drop down list to just active employees in the future?
If I understand this correctly. Yes the feature is already there. Check under employees. When you open the employee that is no longer working. There is a tick box to make employee inactive. Then they will not show on the drop down. Same goes for inventory and some others as well.
Unfortunately not true. This is why I asked Lubos the question.
Fixed in the latest version (15.0.59)