On one of our model we have one “Structured text” field named “body”. On that structured text field we have added one block model(named “Image block”) on the part: “Specify the blocks allowed in this field”.
On that block model(named “Image block”) we have only one field of type “Single asset”.
If we add image through that block model named “Image block” on body, then a preview is shown. On the single asset we have “Title” and “Alternative text”. Can we control to show “Alternative text” below the preview on the body?
Unfortunately, the only way to change that text is to change the title.
To change the title, you will do that very same update request through the CMA, but instead of updating the alt, you would update the title parameter.
As a side note, if a title is not specified, the alt will be used as the caption