Being a Sound Forge user since 2007, I also missed the ‘return cursor to start of playback’ function; just as much as I miss the ‘pre-roll/post-roll skip selected region function’, which Wavelab LE doesn’t have.
At first I thought that Raphie’s solution - hit ‘Page Up’ after stopping - worked; but actually it just moves the cursor to the left.
Alternatively, I found that the first time you click on the stop button, the cursor stops. If you click it a second time, it returns to the last start position. If you click it a third time, it returns to the start of the file. But that’s not quite as convenient as snapping back to the starting point at stop with the space bar.
I also noticed, later, that if you click on ‘Tell Me More’ in the info window when hovering over the stop button, there is a note saying that if playback is already stopped, hitting the stop button again takes the cursor back to the previous start position.
By the way, right-clicking on the stop button doesn’t do anything on Windows 10.
Audio Montages are possible: just create a new Audio Montage project (File > New > Audio Montage); but you’re restricted to only two stereo tracks on LE 9.1.