+1 for the main idea.
Basically it would, by allowing to hide column browser item list, help users to use the limited vertical space on a widescreen display a lot more efficiently.
Here are a few suggestions from me:
- When hidden (not closed), it should look like this.
By displaying two rows (column header and currently selected items) of column browser, the user can be always aware of the currently applied filters and change them easily.
- Double-clicking on column header would toggle to show/hide (not open/close) column browser.
- Clicking on each selected item area would pop out the item list of each column and let the user change the selection.
- All other functionality would remain the same.