$WW,1$There is a symbol (hash) tables for each task.  When a sym is not found, the parent task's sym table is checked.  All tasks chain back to the $FG,2$Adam$FG$ task.

TempleOS sym tables are implemented with an array of linked-lists.  A num is generated from a string by $LK,"HashStr",A="MN:HashStr"$() to index into the array of linked-lists.  Multiple strings can generate the same num, so linked-lists are built.  Newer entries overshadow older ones.  There are various types of entries.  See $LK,"Hash Entry Types",A="MN:HTT_EXPORT_SYS_SYM"$.