I am trying to set two parts a certain distance apart in my assembly, but smart dimension is greyed out. I can't figure out how to change it from driven to driving. All the advice I find online is from SW 2013, and I am on 2021. I can't find a Dimension Tab anywhere. One forum showed a little padlock symbol, which I can't find anywhere either. How do I go about adjusting the value of a dimension to change the distance between two parts?