Luke wrote:As I said this should be changing in a future 25 update - I can't say for sure it will happen or when it will be though.
Can I suggest this feature for v26?
Unless I'm wrong, I can confirm that up to this date Graphisoft HAS NOT fixed this. I tried to merge a list of items while maintaining the first parameter as the criteria for main segregation but Archicad 25 simply merges everything regardless of the fact that the parameter has a different value for the items.
I experimented with this a little bit and when I used an internal parameter of a Library Part as a Schedule Field (as I think you have done) it gave me the same results as for you.
However, if I used the Element ID field for the headline, then it gave the correct results. (Maybe the Headline does not even need to be activated so the Element ID and the Subtotal will be in the same row.)
So this Merging/Summing combo does not work for some reason with Library Part internal parameters.
I will report this to Graphisoft as I cannot decide if this is intended behavior or a bug.