How to modify arrow path?

How to have arrow 2 have the same shape as arrow 1?

enter image description here

digraph {
	rankdir=LR
	label = "Lý thuyết ý định hành động";
	labelloc = t
	labeljust = r
	fontsize = 20
	fontname = Lato
	overlap=false;

	a [ label = "Thái độ của\nbản thân đối\nvới hành động" ]
	b [ label = "Cảm nhận về\nthế nào là\nchuẩn mực" group=g1]
	c [ label = "Cảm nhận về\nkhả năng đạt\nđược kết quả" ]
	
	d [ label = "Có ý định hành động" group=g1 style=rounded shape=polygon ]
	e [ label = "Thực sự hành động" group=g1 style=rounded shape=box3d ]
	
	{ rank=same; a, b, c }
	a:w -> b:w [ label="" dir=both]
	a:w -> c:w [ label="                 " dir=both]
	b:w -> c:w [ label="" dir=both]
	a:e -> d:n [ label="1" ]
	b:e -> d:w
	c:e -> d:s [ label="2" ]
	d -> e
	c -> e:s [style=dashed dir=none]
}

One person suggests me to change c -> e:s [style=dashed dir=none] to c:s -> e:s [style=dashed dir=none]. This works for them but still not for me. That’s strange. We both use version 2.47.1. My command is simply dot -Tpng input.gv -o output.png

By the way, the left arrows can only be that symmetric when I put empty labels to them. Is there any explanation for this?

On my monitor node a is 3mm wider than nodes b, and c. This tiny size difference can be throwing off the symmetry you seek. You can try making nodes a, b, and c a fixed size as I have done below. I also added the port from c to d, i.e. c:s -> e:s [style=dashed dir=none]

The source is as follows:

digraph {
	rankdir=LR
	label = "Lý thuyết ý định hành động";
	labelloc = t
	labeljust = r
	fontsize = 20
	fontname = Lato
	overlap=false;

	a [ label = "Thái độ của\nbản thân đối\nvới hành động"  width="2.0" height="1.2" fixedsize="true"]
	b [ label = "Cảm nhận về\nthế nào là\nchuẩn mực" group=g1 width="2.0" height="1.2" fixedsize="true"]
	c [ label = "Cảm nhận về\nkhả năng đạt\nđược kết quả"  width="2.0" height="1.2" fixedsize="true"]
	
	d [ label = "Có ý định hành động" group=g1 style=rounded shape=polygon ]
	e [ label = "Thực sự hành động" group=g1 style=rounded shape=box3d ]
	
	{ rank=same; a, b, c }
	a:w -> b:w [ label="" dir=both]
	a:w -> c:w [ label="                 " dir=both]
	b:w -> c:w [ label="" dir=both]
	a:e -> d:n [ label="1" ]
	b:e -> d:w
	c:e -> d:s [ label="2" ]
	d:e -> e:w
	c:s -> e:s [style=dashed dir=none]
}

and using v2.47.0 on Windows creates the following graph:

I hope this helps,
Jeff

The length of the label is what is affecting the symmetry. You can achieve symmetry by using xlabel instead of label. For example:

a:w -> b:w [ xlabel="this is a really really really long label" dir=both]
a:w -> c:w [ label="                 " dir=both]
b:w -> c:w [ xlabel="short label" dir=both]

This change makes the graph appear as follows:

If I remove the numbering, I still need to label the arrow 2 as " " to have it the same path as 1. I also prefer to have c:e -> e:s instead of c:s -> e:s, since it would take much less space. Even c:se -> e:s still reforms the arrow 2.

I also find a weird bug. In the code, the arrows between node a, b, c (all the left ones) should have both directions. But in images it is not that case. I have to swap the attributes from label="" dir=both to dir=both label="" to have both directions again.