Jürgen,
you just found some packages to support this character:
http://wiki.lyx.org/LyX/MissingUnicodeCharacters?action=diff#diff1309586810
I tested this and the attached patch works fine. Can this go in or is there a reason why you did not
commit this yet?
regards Uwe
diff --git "a/C:\\DOCUME~1\\usti\\LOCALS~1\\Temp\\uni43.tmp\\unicodesymbols-b64d17e-left" "b/D:\\LyXGit\\Master\\lib\\unicodesymbols"
index 74fbc73..3f38ea7 100644
--- "a/C:\\DOCUME~1\\usti\\LOCALS~1\\Temp\\uni43.tmp\\unicodesymbols-b64d17e-left"
+++ "b/D:\\LyXGit\\Master\\lib\\unicodesymbols"
@@ -1859,6 +1859,7 @@
0x2197 "\\textglobrise" "tipa" "" "" "" # NORTH EAST ARROW
0x2198 "End" "" "notermination=text,tipashortcut=\\textglobfall{}" "\\searrow" "" # Qt::Key_End, SOUTH EAST ARROW
0x21a8 "{\\ascii\\ETB}" "ascii" "" # UP DOWN ARROW WITH BASE
+0x21af "\\Lightning" "marvosym" "" # DOWNWARDS ZIGZAG ARROW
0x21b5 "{\\Pisymbol{psy}{191}}" "pifont" "" # DOWNWARDS ARROW WITH CORNER LEFTWARDS, Return key
0x21de "Option-Up Arrow" "" "notermination=text" "" "" # Qt::Key_PageUp, UPWARDS ARROW WITH DOUBLE STROKE = page up
0x21df "Option-Down Arrow" "" "notermination=text" "" "" # Qt::Key_PageDown, DOWNWARDS ARROW WITH DOUBLE STROKE = page down
