Hello, is there a way to use a column from the top item in the subitem formula ?
No. But, maybe.
You can’t directly address a column from any other item in relative terms, even subitems. However, to can reference column values from linked items by using mirror columns. Usually, the connect boards column is used to link to different boards. But, they can also be used to to link items within the same board or subitems.
So, depending on the details of your use case, it may be possible to link to the item that you want to reference either through the use of automations, a tool like Integromat or a custom app.