How to export annotations from mobi/epub files?
OK, this might not be really relevant to this post, but for other FBReader users who are stuck at the same, I'll share my (rough) solution:

Note: This should be specially relevant to Icarus eReader users! Icarus e-ink readers come with a modified version of FBReader 2 which is pretty stable on that device but unfortunately very basic too. And you can't even update it! I don't know if newer versions of FBReader can do this by default - sorry if this is obsolete information to most of you.


Using a file manager with root access on your ereader (I use Solid Explorer) , navigate to /data/data/org.geometerplus.zlibrary.ui.android/databases/
Select the books.db file and copy it to a non-root directory (like for example to /sdcard/) that you can later access from your computer.
On your computer, open books.db with SQLiteBrowser (you can't just open a .db file with a text editor, you'll see unreadable code). I guess you can perform this step directly on Android with Sqlite Viewer for Android, but I haven't tried that yet.
In SQLiteBrowser, go to the Annotations table of your database and you'll see all your highlights. SQLB is not the best app for editing text, but there's a few export options.


There you go!