Hear me out. When Mario activates a regular goal tape, the checkered box become green. Normal. When Mario activates goal tape 2, goal tape 3 or goal tape 4, the key icons are colored properly. Also normal. When Mario for example activates the secret exit via key and keyhole, the key icon(number 1) isn't properly colored. It remains outlined. Perhaps there should be disassemblies for goal tapes 2, 3 or 4. Perhaps like this, there can be made key and keyhole sprites that activate such exits.
Code
$00C9FE 3 bytes ASM [8D D5 0D] The code itself stores either 01 or 02 to $0DD5. Change to [EA EA EA] to make it possible to set the normal/secret exit info through $0DD5 via LevelASM, sprites, etc. (Note: To activate any exit at all, $0DD5 has to be explicitly set to 01 or 02. Leaving it as 00 will cause no exit to be activated at all, and values 03-FF should not be used.)