To manage the set of named paragraph macros in a section.

§1. We store these like so: 

    typedef struct para_macro {
        struct text_stream *macro_name;  usually long, like "Create a paragraph macro here"
        struct paragraph *defining_paragraph;  as printed in small type after the name in any usage
        struct source_line *defn_start;  it ends at the end of its defining paragraph
        struct linked_list *macro_usages;  of macro_usage: only computed for weaves
        MEMORY_MANAGEMENT
    } para_macro;

The structure para_macro is accessed in 2/pn, 3/tw, 3/tt, 5/ptf, 5/tf, 5/hf and here.

§2. Each section has its own linked list of paragraph macros, since the scope for the usage of these is always a single section. 

    para_macro *Macros::create(section *S, paragraph *P, source_line *L, text_stream *name) {
        para_macro *pmac = CREATE(para_macro);
        pmac->macro_name = Str::duplicate(name);
        pmac->defining_paragraph = P;
        P->defines_macro = pmac;
        pmac->defn_start = L->next_line;
        pmac->macro_usages = NEW_LINKED_LIST(macro_usage);
        ADD_TO_LINKED_LIST(pmac, para_macro, S->macros);
        return pmac;
    }

The function Macros::create is used in 2/tp (§1.1.6.4).

§3. Paragraph macro search. The scope for looking up paragraph macro names is a single section, not the entire web. So you can't expand a macro from another section, but then again, you can use the same macro name twice in different sections; and lookup is much faster. 

    para_macro *Macros::find_by_name(text_stream *name, section *scope) {
        para_macro *pmac;
        LOOP_OVER_LINKED_LIST(pmac, para_macro, scope->macros)
            if (Str::eq(name, pmac->macro_name))
                return pmac;
        return NULL;
    }

The function Macros::find_by_name is used in 2/pn (§1.1), 3/tw (§1.3.3.1.9.6), 3/tt (§3.1).