I have found that LibreOffice does not understand '<mspace width="2.0em">',
comparing the following MathML texts (copied from the unzipped odt).

Therefore, I must accept that LibreOffice does not correctly interpret \qquad
or that at least, '<mspace width="2.0em">' is an unimplemented instruction in LibreOffice.

## Markdown source

    For example, the \qquad in the following equation is ignored:

    $$ y = mx + b \qquad (1) $$

    Y otra ecuación sin el espacio qquad para cotejar diferencias:

    $$ y = mx + b (1) $$

## Results

This is what Pandoc produces when the ecuation has \qquad:

<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>y</mi><mo>=</mo><mi>m</mi><mi>x</mi><mo>+</mo><mi>b</mi><mspace width="2.0em"></mspace><mo stretchy="false" form="prefix">(</mo><mn>1</mn><mo stretchy="false" form="postfix">)</mo></mrow></math>

And this is what Pandoc produces without \qquad:

<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>y</mi><mo>=</mo><mi>m</mi><mi>x</mi><mo>+</mo><mi>b</mi><mo stretchy="false" form="prefix">(</mo><mn>1</mn><mo stretchy="false" form="postfix">)</mo></mrow></math>

And this is what I got using the '~' space command with LibreOffice:

<?xml version="1.0" encoding="UTF-8"?>
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mrow><mi>y</mi><mo stretchy="false">=</mo><mi>m</mi></mrow><mrow><mi>x</mi><mo stretchy="false">+</mo><mi>b</mi></mrow><mspace width="16em"/><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><annotation encoding="StarMath 5.0">{y = m x + b ~~~~~~~~ $ 1 $}</annotation></semantics></math>