As per the topic, it doesn't seem possible to manually create a bookmark. You can only make a bookmark from an existing entry (e.g., a shoutcast entry). But some stations aren't in shoutcast and I'd like to add them manually.
Was bugging me too.
As workaround I always duplicated an existing entry, and then edited the fields.
The original edit window mockup had a button, but I ended up not implementing this.
Also we need some way to IMPORT .m3u and .pls and .xspf bookmarks.
And drag and droping a bookmark INTO streamtuner2 should work as well.