Besides the given formula sheet, you should essentially memorise any formulas that you feel would be difficult to remember.
Additionally, I think it would be a good idea to memorise formulas that are obtained from another formula that you feel you might not be able to remember. For example, is not included in the formula sheet, whereas a formula like is included.
I think another thing to consider would be more basic formulas that represent fundamental syllabus concepts/definitions - those are not included in the formula sheet either. An example is D = ST.
I also suggest taking a look at this document from NESA explaining the bases for the development of the Reference Sheet for use in Mathematics Standard 1 and Mathematics Standard 2 as I believe it would also be helpful in determining which specific formulas you should prioritise/focus on: