Aggregate timelines mirrored columns from different boards

Hi guys,
Appreciate your help :pray:

So I have master board with 2 timeline columns mirrored from two different boards, and I would like to create another accumulated timeline column that sums and aggregates the two other columns.

Timeline column 1 (mirrored from board X) 01/01/2022 - 02/01/2022
Timeline column 2 (mirrored from board Y) 01/15/2022 - 02/15/2022
Timeline column 3 (The one I’m trying to set) 01/01/2022 - 02/15/2022

Thanks again, Ryan.