You are browsing the old Contao 3 extension repository. Contao 3 is no longer maintained as of June 2019! You can find the Contao 4 extensions on extensions.contao.org.
Extensions > MultiSelectWizard
Lets you have multiple select fields per column and row
This widget is actually a replica of the moduleWizard (where you assign different modules to sections in your page layout) which is unfortunately not reusable for other developers as the source (SELECT * FROM tl_module) is hardcoded.
That's why I wrote this widget to make it useful for everybody.