Column Resizing For Groups and Nested Tables

[RamlahAziz]

Is your feature request related to a problem? Please describe.
We are using collapsible nested tables for our customer facing UI. We are also making use of the groups feature to group columns together. We are using fixed widths to match parent and child column widths. But this means that some data gets truncated. We would like to use the resize functionality - but when we resize the parent column, the child column mismatches and leads to broken UI. Also the resize icon does not appear in the title cell in the group, and with only one column - this is not where a user would expect it to be.

Describe the solution you'd like
I would like the resize icon to appear in the top title cell in groups (with one column) or an option of this sort.
I would like to be able to match parent and child column widths.

Describe alternatives you've considered
I tried setting the keys of both tables to the the same key, but since column accessors are different, that did not work.

Additional context
Resize bar appearing in column name instead of top group

Resizable columns mismatch

Is this feature expected anytime soon?
Would also be interested in contributing to a PR if something like this is coming up.