The documentation says you can save a workspace, but I can find no information on how to do so.

They are apparently .pws files, and the documentation explains how to import them, but how do you export them?

Thanks.

The simplest way to save/export a workspace .kws file is to copy it from the .../workspaces folder of your krita configuration storage area. This folder contains any personal workspaces you have created, not the set of workspaces that krita comes with as standard. However, you can save a standard workspace arrangement under a new name if you like, using the 'Choose workspace' icon facility.

If you want to share/distribute your personal workspaces, the 'proper' way to do it is by making a bundle, using Settings -> Manage Resources, then Create New Bundle. You can package all sorts of things into a bundle, including the standard Krita workspaces, brush presets, etc.

The file extension is .kws, btw.