I've added an extra parameter for the next release to "Pick Nth child" so you can choose whether the index is relative to all children (as it works now), or filtered to only the chosen object type (so it works like you want it to here). But I'd note this filtered mode actually works inconsistently to the other existing features - for example the 'Compare child count' condition and 'ChildCount' expression work with the list of all children. There is still no way to compare the child count of just one type of child, nor does there seem to be any good way to design an expression that returns the child count of just one given object type, as the current design of Construct does not allow an object type to be passed to an expression. So while the next beta allows you can pick from a filtered list of children of a given object type, there is no way to identify how many children there are of that type, nor is there any obvious way to design such a feature at the moment. I suppose if you have a fixed hierarchy setup, such as every hierarchy has both two arms and two legs, then picking Nth child with filter may be good enough, but usually I'm pretty reluctant to introduce feature inconsistencies like this - eventually someone else turns up and says "this mode is inconsistent/incomplete, it shouldn't be designed like that..." and we have a similar discussion like this again.