Can I safely use a Nikon Sb26 on an Olympus Trip 35 via hotshoe?
No clue. The trigger voltage is the issue here and Nikon speedlights tend to be quite low to protect their cameras. Have a look here:
Yes, you can safely mount an SB-26 on a Trip.
The problem arises when old strobes are used on newer electronic shutter cameras that use a transistor to trigger the strobe.
f-Stop Timers - Enlarging Meters