I need to be able to collapse nested headers and then get which nested header was collapsed so i can change data in the remaining column that does not collapse. Is this possible/does the question make sense? Any help would be much appreciated.
I have a demo for collapsing headers http://jsfiddle.net/e6x5jm7f/ however we do not have a collapsing hook yet.
You can track progress on the hook at https://github.com/handsontable/handsontable/issues/4873