Getting there...slowly.
I see that tags are in .vtg files.
I created a new one as a sibling to tcl.vtg 
i.e. c:\vslick\tagfiles\myTclOO_tags.vtg... 
as another child file under '"Tcl" Tag Files'. 
I rebuilt the tag file and it seems to have all expected tags.
Re adding tclOO classes...this looks very helpful....
halfway down the page....
Step 6: Write tagging support for Logo
http://blog.slickedit.com/2008/05/tutorial-adding-language-support-to-slickedit/Presumably it's slick-c and I'm guessing the compiled c is what I'm seeing in the .vtg file...It seems to me I need to edit the procs shown for my class and compile them to a .vtg file...Is that it...I must confess I am a bit confused.
Again any pointers would be most welcome.
Thank you in anticipation.