Is there a generally agreed short notation for "a points to b"
The problem with your question is that pointers and pointers semantics
may vary significantly from language to language. Even your question
is ambiguous. So you are asking a question about notation, i.e., about
syntax, which is largely a matter of arbitrary convention, but it is
not even clear what is the semantics intended by your question.

You apparently use as synonyms "a points to b", "a is a pointer to b",
"a -> b". But I am not sure what is the meaning and context. Does it
assert that a is actually pointing to b (descriptive meaning) or
does it modify the data so that a is now pointing to b (imperative
meaning). Then what is b, or what can b be. Is it the location of
some value, or is it the value of whatever is pointed by a. Is it
intended to be part of a programming language syntax, or of the
metalanguage used to discuss about programs.

If you have a -&gt; b and c -&gt; b, does it imply that a = c. Furthermore, if a and c are pointers, what is the meaning of
a = c? See for example "shallow and deep equality".

Actually all this is often an issue of designation of container and
content. A pointer is a designation for a container (a memory
location, for example), and the content of that container may vary.
But the content may also include container designation.

One major problem is that notations are often ambiguous as they often
do not clearly distinguish between container and content, often implicitly
casting one into the other.

If you consider a variable, say an integer variable x in some
programmning language, this variable is actually a container where you
can change the content (which is supposed to be an integer). But,
within the scope of its declaration, x will always be the same
container. An integer variable is actually a pointer constant: a
location designator.

Then, can you write x -&gt; 3 to indicate that x denotes a pointer
constant toward a location containing the value 3?

Or is the arrow supposed to point on the right to whatever container
is "designated" by the expression on the left. But if you have a
pointer constant (i.e. a pointer value) on the left, what is the
meaning of the notation.

Now, you can have pointer variables, which may contain a
container. They can appear through explicit declaration, or via other
mechanism such as parameter passing by reference.

When sharing a meal with other people, you can ask for the bottle or
for the wine. It will mean the same. But in programming context, more
precision may be needed.

So my first reaction to your question is: Could you be more precise
about the semantics you intend to express, before you suggest agreeing
on a standard notation?

Another minor point is that, while asking your question, you seem to
suggest that a double shafted arrow =&gt; would be better than a single
shafted on -&gt;. But you do not give any hint as to why it might be
better. This makes me uneasy, especially wen I am not even sure of
what you want to talk about, and in what context.

Since this is supposed to be an answer rather than further questions,
I would suggest that the lack of a standard may well come from the
fact that programming languages vary significantly in their use of
pointers, and on the semantics attached to various constructs using
pointers. We can hardly standardize notation when what is to be denoted is
not itself standardized.

Hence, our only recourse is to choose for ourselves a notation that is intuitive and
consistent in its intended context, and define it precisely together
with the associated semantics. I insist on consistency since there are
many things you may want to do with pointers, and it is important
that the notations for each remain intuitive, and that they combine
naturally and consistently. The issue of equality is an example.