Alternative text
You can define text alternatives in the properties of elements that use images. Text alternatives are displayed instead of the image in non-image-capable devices, for example.
Simply enter the desired text here as static text. Information on multilingual texts can be found here.
Depending on from where you access this dialog, e.g. from a button with the button type "Image", a data field can be selected here as the text source for the dynamic display of the desired text.