Multiple views of same project data with summary bars

I have inherited a GANNT smartsheet with activities structured by vendor, so each vendor has activities for every project phase. I now want to use the same data to present an overall project view summarised by project phase, with the vendor bars below. The summary bar would be duration for the project phase, rolling up dates from the vendor activities below. I can't quite see how to do this using reports or copied rows. I can add a 'Phase' column, and then report by phase - but not get a rolled up duration, or a report containing all project phases