Aside from medium/high issues, you might want to visit this topic and see what plugins were requested the most. Of course, if you develop a plugin, this won't be a direct contribution to Joplin core but still a very welcome addition. I think this is what @roman_r_m meant.
In some cases, features done via plugins are even preferable (compared to direct change in Joplin core) due to less maintenance needed from Joplin team.