It does show SK8, which, although it's not obvious from looking at it, was a Lisp environment.
It was implemented in Common Lisp--specifically Macintosh Common Lisp, which is the direct ancestor of Clozure Common Lisp--on the pre-OSX Mac system. That's sort of obvious if you look at the menubar in Slide 7.
The ScriptEditor shows a snippet of SK8Script, which was the first working implementation of AppleScript. SK8 compiled SK8Script to Common Lisp, and thence to native code. The runtime underneath was Macintosh Common Lisp, and you could open a Lisp listener window or editor window if you wanted, and work directly in Lisp.
The funny-looking window design has a practical purpose: it doesn't look like any other widely-used window design, which means that when you used SK8 to create a Mac application, the SK8 tools always looked distinct from all of the application windows that were under development.
The funny-looking windows are notable in another way: their non-rectangular outlines required a custom code resource (a WDEF), which you could write in Lisp with MCL.
As with all of the other environments illustrated in these slides, there are lots of details that are not obvious from the image. This sample screen shows someone in the middle of constructing a working giant scrollbar by snapping together boxes and arrows and editing scripts attached to them.
SK8 was very direct-manipulation-oriented. You could do a lot of stuff by dragging objects onto the screen, snapping them together, and opening inspectors to edit visual properties, event-handlers, and attached behaviors. You could grab an arbitrary screen object and drop it into a message box to get an expression that, when evaluated, yielded a reference to the dropped object.
It did a lot with containment--for example, you could put objects on the screen by adding them to a container called the Stage, and there was a containment hierarchy that routed events to handlers. The model was extremely flexible; for example, you can see in the Script Editor that the programmer wants an event to set the fillcolor of rj1 to green, but Dave Yost (one of the SK8 authors) used to like to demonstrate setting the fillcolor to a Clint Eastwood movie, which would then begin playing in the background of the targeted object.