I am using 1024set screen.
The "Spindle CW F5" button to which you refer seems to turn on the spindle clockwise. The yellow led seems to continue to flsh. If you press it a second time, it turns off.
If you compare it with the "Spindle toggle" on the diagnostics page, this does the same, but the yellow led only flashes once.
The two yellow leds are, however not the same function. One is oem 11, the other code 813. 11 is Spindle CW (which I assume means clockwise) and 813 is spindle dwell.
I must report that mine turns the spindle off, and the led stops flashing.