Last week we discussed this some more internally and ended up where the consensus was that there’s no way around adding outlets at the moment — so now we have:
before-sidebar-section and after-sidebar-sections available as outlets
If the need is to add a custom section of links that mirrors the layout of existing link sections, the recommendation is to still use the API so we can maintain compatibility if the sidebar changes in the future. If this part of Discourse were to change again (no current plans) we can’t promise that the plugin outlets would neatly be migrated over like we can with an API.