Watermark effect with coordinate positioning without x:y

Problem/Motivation

\Drupal\iek\Plugin\ImageEffect\ImageWatermarkEffect::getAlignPositions
contains "coordinate", but the form does not contains input elements for x and y.

Resize effect is similar, but works in a different way. (I think this one is implemented in a correct way)
\Drupal\iek\Plugin\ImageEffect\ImageResizeEffect::buildConfigurationForm