If you use the sidebar documents list you can turn off the tabs and get back precious vertical real estate.
It has been pointed out that this may not be clear, so to expand:
The "Documents" sidebar tab has the same functionality as the notebook tabs, and since its vertical not horizontal it can show many more files than the tabs can before scrolling is needed.
Since it has the same functionality, when it is in use the tabs are redundant, and can be turned off (Edit->Preferences->Interface->Notebook Tabs->Show Editor Tabs) to get some vertical space back (especially on systems where the theme makes tabs very high).
When the tabs are turned off, rolling up a directory in the Documents tab is effectively hiding those files as the OP requested.