How can I add an arrow in a specif vertex?
If you mean "can an arrow be added to one of the lines that make up a shape" then the answer is no.
It might be possible to add a line to the shape, add the arrow to that line, then group the shape and line, but that does depend upon the original shape.
Line patterns may help.
http://visguy.com/vgforum/index.php?topic=7745.0
http://visguy.com/vgforum/index.php?topic=1893.0
I assumed Lmontenegro wants to add an arrow to just one vertex of, say, a rectangle.
I assume that Paul is correct. There is another method which doesn't require grouping, but does require editing shapesheet.
Open shapesheet, add another geometry section. In this section, set Geometry.Nofill = true. Then, in first row (move to), enter x,y- position of some starting point, perhaps a vertex from Geometry1 section. In 2nd row (line to) enter x,y-position of desired vertex from Geometry1.
Then, go back to drawing page, and select the desired ending arrow type.
This can be made more dynamic to go to any vertex by adding another section to the shapesheet, the Controls section. Add two controls. One for the line starting point and one for the line ending point. Reference the Geometry2 line to these control points.
Now when you select the shape, you can move the control points to wherever you want, and the line will follow.
The line end arrow will effect all lines in all geometry sections of the shape, even though for a closed shape those line ends won't show!
Yep. The key point, the arrows don't show on the closed shape...which is why we're doing this in the 1st place.
Both methods have caveats. For my proposed approach: all line features including color style, weight, etc are inherently identical. It forces a common uniform structure. If that's not desired, then grouping approach needed. All so, the coordinate basis is common...doesn't require going to 3rd party (the group) to sort out sub-member locations. And, the control points make placement very easy/simple. How's that "sales pitch?" LOL