dhtmlx-compat does not translate the span key '{key}', so it has no effect. Lattice spans carry only geometry (rowspan/colspan); the cell's value, css and tooltip come from its own column, not the span.

Warnings reference › dhtmlx.span.dropped:*

Identifier

dhtmlx.span.dropped:*

Raised by

dhtmlx-compat

Since

1.20.0

What happened

addSpan() was called with a key beyond the four the shim understands (row, column, rowspan, colspan). In dhtmlx a span can also carry the merged cell's text, CSS and tooltip; in Lattice a span is geometry only and the merged cell renders through the column it belongs to, so those keys had nowhere to go.

The fix

Set the appearance on the column instead - its cell.render, its cell.class, its tooltip - and keep the span for geometry.

The smallest fix

grid.spans.add({ row: 3, column: 'name', colspan: 2 });

Reference

Covered in full at the API reference.