Roll up sub item without an additional column

I understand that I can reflect items from the sub items onto the parent item by rolling up the column to the item. However, with a lot of columns, this is taking up additional space. Could we somehow have a mirrored column between items and subitems? or perhaps a way to reflect data in the same type of column in a sub item up to an item?

2 examples:

I have a column called “actual hours” which is a numbers column. I also have that column as a sub item column. I can keep track of planned time and add it to the parent item, but it would be cool if I could have the option for it to be done automatically.

Second example would be a timeline column. If I have multiple subitems under the parent item with timelines, I should be able to roll them up the same way with with mirrored timelines with the earliest to latest date.

The app Rollup Subitems can rollup a subitems column (e.g. “Actual hours”) into an existing parent column (in this case a number column). It can also filter to allow different views to the subitem columns (e.g actual hours per month)