Feature request: Re-order table columns

[Novark]

It would be great to have the ability to re-order the position of columns in the Data Explorer - in a similar manner to how most operating systems allow you to re-organize and re-order columns in the file explorer.

Right now, they can be re-sized horizontally, but not re-positioned. Sometimes I want to group columns together so that they are displayed in a logical grouping.

Semi-related: Issue #35