It is a small thing, but I would like to be able to close all open tabs in the workspace with one click. I would think it would be added to this drop down, in the attached screen shot. But whereever ...
RIght click on any tab in that workspace and select one of the "Close" options there. I, personally, use the "Close all but this one" option.
You can also set your maximum number of open tabs under Tools | Options | Panels | Workspace. I find 20 tabs to be excessive. I rarely need that many open at a time, if ever. Usually I set that value to 10 as being a manageable amount. When you exceed that number, TestComplete will auto-close a tab, prompting to save if necessary. Give this a try.