Hi Jonas and welcome to the Silverfin Developer Community! 
Not sure what the current code of your template looks like, but if you structure the content in an HTML table, you can add classes to cells that will make whatever’s in them justified (or aligned any way you prefer).
You can read more about alignment in HTML tables here.
And if you need some tips on how to transform a markdown table into HTML, you can also check out this case.
Apart from using HTML tables, it’s not possible to make text justified in Silverfin. Though it may look like text is justified in export sometimes, that’s actually just spacing because of long words that are being forced onto a new line.
Kind regards,
Romy