Since you mention Dired+, Menu-bar menu Dir, submenu Navigation has these items, with associated keyboard keys:
Next Dirline (>)
Prev Dirline (<)
Next Subdir (C-M-n)
Prev Subdir (C-M-p)
Up Directory (^)
Tree Up (C-M-u)
Tree Down (C-M-d)
Move To This Subdir (i)
C-M-u and C-M-d are the same in vanilla Dired. Vanilla Dired also offers (less useful) ...
To discover an existing command that moves up or down lines, use command apropos-command, bound to C-h a by default.
Commands involving lines often have line in their name. So try that: C-h a line RET. Among the displayed command names and their descriptions, you'll find next-line and previous-line.