From the main menu there is a Project/Properties selection, i assume that is what you refer to? It has a "project's dependencies" button that brings up a small dialog in which the library is checked.
From the Project/Properties dialog which has the "project's dependencies" button, one can also select the "build targets" tab, which shows the builds (debug/release) on the left, and has a "Dependencies" button; when clicked that brings up another "external dependencies" dialog where one can add/edit either "additional output files" or "external dependency files". The library is also listed there as an "external dependency" file.
The word "dependency" seems to have (at least) two meanings, one meaning pre-requisite projects, the other meaning files required by the link. I admit to finding this somewhat confusing.
When building the executable from within c::b there are no apparent issues. But the makefile generated for the main project (the executable rather than the library) does not also build the pre-requisite library. It knows it should, but has no rule telling how it is to be built. Theoretically if c::b builds the library and the executable when a library member has changed, it seems like the makefile should do the same thing.
It isn't and i'm not sure why. Thanks.