Sub-layout type "Stack X" unavailable when linking data to y-axys

Hello everyone, I'm experimenting with the Charticulator preview embedded in Power BI as I'd like to design a dual y-axis symbol and bart chart  (basically the same that can be obtained in Excel by combining bar chart and a scatterl plot). In order to do so, I created two glyphs so that I could set up two plot segments, each one with it own y-axis. However, whenever I try to assign data to any of the y-axis, the sub-layout in the attributes tab of the plot segment does not allow me to choose the one that I want, that is "Stack X". Instead, I get to choose only between "Overlap" and "Packing". I also tried to add a data axis and then use it as a y-axis by dropping the values I'd like to see on the data axis, but I noticed that data axis are not linked to the height of the bar chart (i.e. the bar chart height can read "50" while the data axys can be any values as it is easily manipulated by hand). 

Does anyone know how to resolve this issue? Many thanks in advance