Don't contact me saying that your smart doesn't have a seat height adjustment handle.
If you look closely at the information in the top left you will see it is ForFour only.
The problem with the original design was that the top of the handle was level with the
side of the seat base, this meant that it was all too easy to catch the edge of the lever
as you sat down. This would dump you straight onto the lowest setting available.
Obviously having to readjust the seat every time you got in was a pain but it
also becomes dangerous when you shuffle during driving, catch the lever and find
you can't see over the steering wheel (all you short arses obviously).
Lever off the cover using a knife or thin blade screwdriver. Try not to damage the plastic.

Using a Torx40 screwdriver, remove the centre bolt. The handle can now be removed.

Due to the way the it is held in place there is only 1 other position the handle can go, see below.

Refit the handle in this direction, refit and tighten the screw and refit the cover.
As quick as a shot almost 2 years later, smart redesigned the handle

You can see that even the flabbiest bum won't touch it down there.
To get one, go to smart and give them one of these numbers depending on what side you drive.
Right Hand Drive - A 454 919 04 61
Left Hand Drive - A 454 919 03 61
These numbers replace the part numbers for the original design.
Fitting of this new handle is the same as shown above, take the cap off,
remove the Torx40 bolt, fit this new handle, tighten and refit the plastic cover.
Job done.