occasionally something I do in the top left will cause what I think is the dash to show everything that is open on every desktop,
similar to what happens when I press cntrl+f8


I have the icon only taskbar set to show only the tasks open on the active desktop, on the bottom panel [which is just how I like it]
I have a few launchers on a left side panel

KDE 4.8.2
Mageia 2

Sorry, what's your question?

If you want to disable it, configure or whatever, look at:
System Settings → Workspace behavior → Screen edges
If you ask me, this is one of really great, but little know features of KDE.

One more time

occasionally something I do in the top left will cause what I think is the dash to show everything that is open on every desktop,
similar to what happens when I press cntrl+f8

how do I reproduce the inadvertent opening of the Dash
somewhere there is a setting, or way to set a shortcut or add a widget/launcher
I sure can't figure out what it is?

This is definitely a KWin action, have you checked the Screen Edges settings as recommended by Minio above?

Thanks
I get it now

when I go to
systemsetting>workspace behavior>screen edges

the action I was trying to describe:
present windows>all desktops
this is handy when you've lost a window & can't remember where