I've had lots of enquiries recently about when Bookmarks and Navigator will have a version available for 10.3 - they've been updated and new features added for every release until now. I'm please to say they will be available with the upcoming version of RAD Studio (10.3.1) which is coming out soon.
The reason for for being included, and for the lack of news about a 10.3-compatible release in the past month, is that the plugins have been acquired by Embarcadero and so will now ship with the IDE itself.
This is great news. I wrote the plugins originally to add features I wanted to the IDE, and hundreds (thousands, actually!) of developers have given great feedback. It's great to know the features will be available to everyone. In addition, due to the pressures of work, I haven't had much time to maintain or extend them recently, and so having them under Embarcadero's wing means they'll live on and be developed as part of Delphi and C++Builder itself.
More info in the linked post!