The pair of symbols that stand for "isomorphic" and "not isomorphic" - basically equality sign with a tilda on top - seem to be conspicuously absent from all the palettes that I've seen. Is it hidden somewhere I failed to find it or actually absent - and if latter, is there any reason for that ? It seems to be a rather basic symbol, especially compared to much more niche stuff in "Relational" palette. 

Another conspicuously absent symbol is "not a subset". We have good old subset, and a "notSquareSubset" but I couldn't locate the "not a subset" in any palette. 

Less critical but still noticeable is absence of various arrows indicating surjectivity, injectivity and bijectivity. 

Is there perhaps a workaround to typesetting all of the above ? Copying from another document works usually but it's not a very convenient way. And if they are actually absent, perhaps we could ask the good folks at Maple to add them for the next update if it's not too much trouble ?

Isomorphism symbol : ≅
"Not a [proper] subset" symbols :  ⊈ ⊄
Arrows : in LaTex, \rightarrowtail \twoheadrightarrow \twoheadrightarrowtail 
Arrows