>> *  « start keyboard navigation with this thread »
>> (InternalThreadNavigationMorph moreCommands ) What is
>> a « thread » in this context ?

You can use an InternalThreadNavigationMorph (ITNM) to create a
sequential suit of projects. In the context of ITNM  we call these suits
<a thread>. 

With the command <start keyboard navigation with this thread> you
can use the right and left keyboard arrows to go from one project to
an other as if these were photo slides.  The command act only on the
current selected thread, as InternalThreadNavigationMorph support the
creation of lots of differents named <threads>. 

Hope this help

Raymond