Thanks for pointing me in the right direction.
I found there are 3 choices that deal with the desktop in MintConfig;
- XFCE 4 Desktop settings
- XFCE 4 MintDesktop (which is the one that enables Compiz)
- XFCE 4 Advanced Desktop effects
So ... Xfce4-MintConfig from the main menu, then select the Desktop tab, then Xfce 4 MintDesktop.
From here you select the Compiz Fusion tab and then you have two choices;
Compiz Fusion (enable/disable)
Compiz Fusion on login (enable/disable)
This XFCE release has me interested in Mint once again