Actually, this is not too hard. The first thing to notice is that [citrus maranta] x [fourpetal maple] is listed three times. So that is the first cross-breed (call it (A))

[[[[fragrant ball cactus] x [[citrus maranta] x [ (A) ]]] x [citrus maranta]] x [fragrant ball cactus]] x [[[[fragrant ball cactus] x [[citrus maranta] x [ (A) ]]] x [citrus maranta]] x [[[[fragrant ball cactus] x [[citrus maranta] x [ (A) ]]] x [citrus maranta]] x [citrus maranta]]]

Then [citrus maranta] x [ (A) ] is listed three times, so that is the second pair, call it (B)

[[[[fragrant ball cactus] x [ (B) ]] x [citrus maranta]] x [fragrant ball cactus]] x [[[[fragrant ball cactus] x [ (B) ]] x [citrus maranta]] x [[[[fragrant ball cactus] x [ (B) ]] x [citrus maranta]] x [citrus maranta]]]

Then [fragrant ball cactus] x [ (B) ] is listed three times, so that is the third, and call it (C)

[[[ (C) ] x [citrus maranta]] x [fragrant ball cactus]] x [[[ (C) ] x [citrus maranta]] x [[[ (C) ] x [citrus maranta]] x [citrus maranta]]]

The fourth cross-breed uses the Citrus Maranta again: [ (C) ] x [citrus maranta], call this one (D)

[[ (D) ] x [fragrant ball cactus]] x [[ (D) ] x [[ (D) ] x [citrus maranta]]]

You may need to grow more than one of (D) since it is now used twice:

[ (D) ] x [fragrant ball cactus] = (E)
[ (D) ] x [citrus maranta] = (F)

will then result in:
[ (E) ] x [[ (D) ] x [ (F) ]]

Cross-breed (D) and (F) to get you (G) and then (G) and (E) will give you the plant you are searching for!