Two versions sharing /home
 

If I create a separate partition for /home, is it possible to use this same directory for two different versions of Slackware i.e. Slackware 10 and Current?

Of course it is possible, I even shared /home this way between a Redhat system and Slackware.

Take care of window manager like KDE that set your preferences in each X session, though

I would use a different user name though. If you use the same user and the same DE you can sometimes run into problems if there are settings that no longer apply (icons as one example). Also you often miss "improvements" in a new version of the DE.

It works but the DE does tend to get confused if you log in as the same user.