Problem:

Is it possible to have text appear horizontally on the left or right sided tabs?

Resolution:

Unfortunately it is not possible to have a 'literal text' horizontally in the tabs, not only in Dialog System but also in Panels2 API. In the past one could do this with OS/2 but then the tabs appeared to be rather big.

The only way to do this is to create a bitmap with a horizontal text and place this on the tab, instead of a 'literal text'.