Therefore sign

Is there any better alternative to the three-dot notation?

The usual general advice is to use words instead of symbols.

The best notation is no notation; whenever it is possible to avoid the use of a complicated alphabetic apparatus, avoid it. A good attitude to the preparation of written mathematical exposition is to pretend that it is spoken. Pretend that you are explaining the subject to a friend on a long walk in the woods, with no paper available; fall back on symbolism only when it is really necessary.

(Paul Halmos, How to Write Mathematics, p. 40.)

This applies particularly to the three-dot notation.

Do not misuse the implication operator ⇒ or the symbol ∴. The former is employed only in symbolic sentences; the latter is not used in higher mathematics.

Bad: a is an integer ⇒ a is a rational number.
Good: If a is an integer, then a is a rational number.
Bad: ⇒ x = 3.
Bad: ∴ x = 3.
Good: hence x = 3.
Good: and therefore x = 3.

Bad Theorem. n odd ⇒ 8|n² − 1.
Bad proof.
n odd ⇒ ∃j ∈ Z, n = 2j + 1;
∴ n² − 1 = 4j(j + 1);
∀j ∈ Z, 2 | j(j + 1) ⇒ 8 | n² − 1

This is a clumsy attempt to achieve conciseness via an entirely symbolic exposition.Combining words and symbols and adding some short explanations will improve readability and style.

(Franco Vivaldi, Mathematical Writing, p. 4 and 132.)

If you are trying to insert the therefore symbol into a Word document

Hold down the ALT key and type 8756

In Excel, select insert, then select Symbol.

Then using the pulldown menu by Font, select Symbol

Type character code 92 in decimal.

You can do the same in Word as well.