I'm working on a spell checker for Silesian. Could you add Silesian (Poland) (szl-PL)? Thank you!
Eike Rathke committed a patch related to this issue.
It has been pushed to "master":
Resolves: tdf#101540 add Silesian [szl-PL] to language list
It will be available in 5.3.0.
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.