Hi @Matthijs,
Of course
Seems to me you forgot to add a result-tag in your template, which make it accessible in other templates.
So you could do this instead:
Nettoresultaat | {{ $10 | currency }} {% results "omzet" $10 %}
and only then will you be able to refer to it in another template as period.reconciliations.Beroepskostentest.results.omzet
Care to give it a go?
More info on result tags here