Hi! 2 days ago I created a library pull request with molded polarized capacitors (CAPPM). Those are often used for tantalum capacitors. Maybe it helps?
A lot of parts (even very basic ones) are still missing because nobody created them yet. For other devices, feel free to create devices according to the library conventions and contribute them to the standard library!
If you create devices or packages that are very similar and that could be generated, check out the https://github.com/LibrePCB/librepcb-parts-generator project.