^ line breaks

I would prefer

USE_QT5= core dbus gui network qml quick widgets x11extras xml \
                 buildtools_build qmake_build

I had this for the git-port of it:
LICENSE_FILE= ${WRKSRC}/COPYING

is the LICENSE file not present in the official release?

^ according to portlint, you should invest in gettext stocks

%%QT_QMLDIR%%/org/kde/latte/liblattedockplugin.so

This is one of those weird cases where my portlint doesn't tell me that. And there was also sayonara, remember, where I added gettext-runtime (because of portlint) and then removed it later because it turned out ot be a false positive and something else was pulling it in already.

MASTER_SITES=        KDE/stable/latte-dock

Don't use MASTER_SITE_SUBDIR.