A link to an ojs3 article has the form https://example.com/index.php/pna/article/view/2 where pna and 2 are the only two variables for the journal. I added
$up = explode('/', $citationData->URL) ;
$citationData->URL = $up[0]."//".$up[2]."/".$up[4]."x/".$up[7] ;
after line 336 in CitationStyleLanguagePlugin.inc.php
and now have a pretty link https://example.com/pnax/2 for the article cite formats, and to make it work .htacces needs following lines:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^/?pnax/(.*)$ https://example.com/index.php/pna/article/view/$1
</IfModule>
You may consider this as a future option to the plugin.