No compress-action pre-built in Thunar
 

In slackware 13 rc1 and slackware64 -current either I'm missing a pre-built action in thunar to create archives. If I want to compress some files I've to start an archiver outside of Thunar. Is this 'normal' or do I have an error in my installations? In pcmanfm there's an archiver well integrated.

I created now in thunar a user-defined action 'compress' (with tar and gzip), so I can start it form the Thunar-menu, but the function is rather basic than a complete archiver-GUI...

This is normal. Thunar is just a file manager and has no archiving functionality built in. However, there is a thunar-archive-plugin that you can add. There is a slackbuild script for it at slackbuilds.org.