When you create the preview window (e.g. by pressing F9) Openbox reads in the sheets and contents of the Excel formatting template file you chose.
In most cases, this is brought in exactly as in Excel. However, in some cases you may not see everything you expect in the preview.
In particular, shapes (triangles, arrows and so on) are not shown in the preview. In most cases, they will be shown in the built model. However, in some cases, complex shapes (with “custom geometry”) will not appear in the built model.