The Translation Memory pane (Studio 2015/2011) sometimes shows a 4th column which can be populated with information like 'Dokumentationsart Betriebsanleitung'. Can I switch this column off to save space?
Yes, by going to "File - Options - Editor - Translation Results Window" and unchecking the option "Show translation unit fields values".
Be aware however that you will not see any field values anymore and will not be able to distinguish TUs with different field values.
If you don't use fields, this is not a problem, but if you do, you will use useful, information.