Insert Markup macro broken on Legacy Editor

Issue Summary

The macro is no longer showing the content preview upon inserting markup coding.

Steps to Reproduce

1. Create a new page using the Legacy Editor template;
2. In the toolbar, navigate to Insert > Markup.

Expected Results

The macro toolbox opens with the insert text box, to write the markup content, and the preview box shows how the content would look like.

Actual Results

Only the insert box is shown, centralized in the macro toolbox.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available