Three levels of subheadings:
Text
behavior 123, 127, 132
blocks 123
editing 124-126
rotating 125, 126, 128-131, 153
bold 107-113, 115
italics 111-115
strings 125, 126
Two levels of subheadings in indented style index:
Text behavior 123, 127, 132 strings 125, 126 Text blocks editing 124-126 rotating 125, 126, 128-131, 153
Unlimited levels of subheadings could mean that four levels is fine:
Text
behavior 123, 127, 132
blocks 123
editing 124-126
rotating 125, 126, 128-129
horizontal 129-130, 153
vertical 130-131
bold 107-113, 115
italics 111-115
strings 125, 126