[LVL ED] Blood ?

[ethics]

YES that what i'm searching for i think i don't have one or i can't find it -.-

It is located in the decals section, which is "0" on your keyboard.
There you can find blood splatters and also the bloody footprints you were talking about.

EDIT:
I just re-read your post and you were saying, that you need a trail of blood.
The level editor doesn' have that, but you can do one yourself: Select a normal blood splatter and place many of them on the ground.
You can also experiment with the size of them, make them more narrow, so it looks like a trail.
Also:
Pro-Tip: Open the maps of the Custom story in which you saw the trail you were talking about and examine it.