This is now implemented by inserting a Read more... tag (the button is located below the editor area) a dotted line appears in the edited text showing the split location for the Read more.... A new Plugin takes care of the rest.
It is worth mentioning that this does not have a negative effect on migrated data from older sites. The new implementation is fully backward compatible.
This is the Popup Module feature. Assign any module to the popup module position, and ensure that the Popup Feature is enabled in the Gantry Administrator.
You can configure its height and width from the Gantry Administrator.
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