Checked using RS_ABAP_SOURCE_SCAN on AS ABAP Developer Edition. At least here the only usage is in the syntax diagram.
BCL_ABAP DOCU SYNTAX_DIAGRAM===CMOOK000273 subrc = sy-subrc.000274
000275 % NON-LOCAL, % PREDEFINED, % PREDEFINED DUMMY, NON-LOCAL in DATA. CLASS-DATA. CONSTANTS, STATICS000276
000277 WHEN 'CLASS-DATA' OR 'DATA STRUCT'.000278 REPLACE ALL OCCURRENCES OF000279 sOptionxsSequencexsNonterminal>DATA PRTVATE OPTSs/Nonterminalxs/Sequencexs/optiony000280 IN Syntax xml wITH .. "% NON-LOCAL, % PREDEFINED, %PREDEFINED_DUMMY, NON-LOCAL000281 subrc = sy-subrc.000282
000292 <Altx<Terminal>%PREDEFINED_DUMMY</Terminalxs/Alt88000293 s/Alternativexs/Sequencexs/option000294 IN syntax_xml WITH NON-LOCAL. % PREDEFINED. % PREDEFINED DUMMY000295 subrc = sy-subrc.000296 REPLACE REGEX