These commands are displayed only if a text layer is present.
In the Text to Selection drop-down list, the commands are identical to those of the Transparency sub-menu (in fact, the text is formed of areas of different transparency):
Text to Selection: Abschnitt 7.38, „Alpha to Selection“
Add to Selection: Abschnitt 7.39, „Add Alpha channel to Selection“
Subtract from Selection: Abschnitt 7.40, „Subtract from Selection“
Intersect with Selection: Abschnitt 7.41, „Intersect Alpha channel with Selection“