I have come across to multiple documents for QtGraphicalEffects, all under 5.12 documentation, and having 3 different versions of QtGraphicalEffects

http://doc.qt.io/qt-5/qtgraphicaleffects-qmlmodule.html
http://doc.qt.io/qt-5/qtgraphicaleffects-index.html
http://doc.qt.io/qt-5/graphicaleffects.html

In one doc, it is mentioned as 1.\1, which seems some typo, but not able to use 1.1 in 5.12
In other, it is 1.12, which seems fine.
The third doc has 1.0, which seems to be fine.

Please check the version supported for 5.12.