The amssymb package has
\leqq. Is there a way to construct
I looked at the amssymb.sty file, and there's not an obvious way to modify the
\DeclareMathSymbol which defines the initial three.
I'm familiar with rough commands to stack symbols on top of one another, but I'm interested in the aesthetics of
\lesscong to "fit" among the initial three. I'm also interested in the slashed and mirrored variants of
\lesscong, but I'm sure I can create those once I have the "parent" construction for
Barely related: A long time ago I wanted to create
\appprox which is three
\sim symbols stacked on top of one another in such a way that the spacing between consecutive two
\sim is exactly the same as the spacing in
\approx. I forgot how I managed to define it, but it may help.
Of course, if I manage to find a nice solution on my own, then I'll post it here for others as well.