Doing help dt in CLI goes to dots.
In the opened list, dots is on the top of the viewport. (Hence dashtype is way above it — in the invisible part of the list.) Without knowing what this abbreviation means, there is no way¹⁾ to guess.
¹⁾ Well, switching to the “Search” mode would really help — but I do not think many people would guess that this is the way to proceed.
(I do not know how to control Window Help to allow “synonyms” [Hey, AI, where are you?!], but at least one can make separate pages for abbreviation.)
FWIW this is not specific to the Windows help, but applies also to gnuplot.gih, gnuplot's text-based help system. Many (none?) of the two-letter acronyms like "pt", "ps", "dt", "lc, "lt", "lw" seem to be indexed.