I've managed to work out how to retrieve the library (fairly obvious, I'm sorry).
But having the workspaces back without having to recreate them would be pretty useful, too.
Workspaces can be copied from version to version (but keyboard shorcuts from CS4 need special treatment if you want to copy them to later versions). You'll find them as .xml files in the Workspaces folder in your user profile/library. For where to look, see Replace Your Preferences. The Worksapces folder will be in the same folder as InDesign Defualts.
Many thanks for that. And I'm delighted to hear that these settings can be retrieved, and especially paragraph and character styles and font choices that all exist as part of a custom workspace. But I haven't been able to follow these instructions to make the replacement.
A search for workspace folders produces several, but non contain an .xml file with any but the standard set of workpace names, and not the custom one.
The paths given to find two files in the document to which you linked, do not seem to exist beyond
There's no 'library' under that category.
What has worked for the desktop is using a search for 'workspace' to find the InDesign Workspace folders for both InDesign CS4 and CS6, and then dragging the en_US folder from one to replace that in the other. CS6 on the desktop now has the library and paragraph styles desperately needed.
However, dragging the same folder from the desktop over to make the same replacement on the laptop hasn't worked, and the same settings are vitally needed there, too.
Any further thoughts would be much appreciated.
Actually, on further investigation, the paragraph styles and character styles have apparently arrived with the documents themselves (I expect that's obvious to most people). The library is also there and can be opened. Just selecting the panes to make a new workspace won't take that long.
In short, it's all more simple than I feared.
But many thanks for the assistance.
My crude drag-and-drop method seems to have worked. But thank you, and your information on hidden files noted for future reference.