The List may not be absolute covers everything, however, studied done on the last 10 years questions depict that WAEC are more focus on the following:

Sets
Constructions
indices, Surd and Logarithm (number less than 1 and greater than 1)
Arithmetic and Geometric Progression
Simultaneous Equation, Quadratic Equation: One linear one quadratic and Quadratic graph
Word problems and Inequities
Statistics and probability
Trigonometry (including graphs) and Equation of straight line or Gradient
Calculus and Matrix
Menstruation (Area, Perimeter, Volumes and Comparison)

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Sources: https://erudites.ng/forum/topic/important-topics-that-waec-set-mathematics-questions-from/#postid-537