I've hacked together a very early version of a chart downloader/updater plugin.
Currently the only chart source supported is NOAA (both raster and vector charts), although it's easy to extend it to support any other chart sets from authors able to pack the charts
individually and produce a simple XML file with the list of the charts
and a little bit of metadata.
There was just a very limited testing, so I suggest you don't point it at your regular chart directories.
Also the functionality relies heavily on file creation dates, so it's not entirely clear how well would it work for you.
If you want the icon in the toolbar as shown on the screenshot, you have to enable it in plugin's settings. There is no functional difference whether you access the plugin through the settings or toolbar.
The preset chart path (.) is the application runtime directory - it is not a good place to keep your charts, please change it before you start clicking on the Download buttons.
The plugin can't do chart database updates, so you have to go to Settings->Charts and click OK or restart OpenCPN
to use the charts you've just downloaded. Also don't forget to add the folders where you download the charts on the Charts tab.
2.4 beta is required.
Precompiled binaries at https://github.com/nohal/OpenCPN/downloads
Just grab chartdldr_pi.dll for Windows or libchartdldr_pi.so for Linux
and place to your plugin directory. Still no Mac here...
Source available as usually at https://github.com/nohal/OpenCPN/tree/chartdldr
Enjoy and report back