Using LDCad

[Philippe Hurbain]

I have simple question, how to adjust shock absorber length
can't find the way how to select and move only one pinhole

Hello - welcome here!
LDraw library provides shortcuts for full length shock absorbers, but as the shortcut is a single part, it can't be directly modified.
The crude way is to replace it with its components (cylinder/piston/spring), an operation known as "inlining" in LDraw jargon. To do that, select the shock absorber, right click then Reorganize -> Inline. You will be then be able to move the components independantly. Drawback of this crude way is that the spring length can't be adjusted.

So the best way is to replace the LDraw shortcut with a LDCad shock absorber template. LDCad dynamically generates a srping of the right length. There is a tutorial for this on LDCad website here: http://www.melkert.net/LDCad/docs/advEdit

Feel free to ask if you need more details!