Do you support multi-line ("stacked") tabs?

No, we don't have any plans to implement the stacked tabs; we're never implementing the extremely non-user-friendly UI. The stacked tabs were popular in the 1990s, but most software vendors got rid of them (MS Office "Options," Windows file properties, Total Commander "Options," Google Chrome, and others). The main problem with this UI concept is the inability to go through all pages sequentially (the pages order changes when the user clicks the tab). If you've got a property sheet with a lot of pages, we suggest using a navigation list on the left (as in the MS Office "Options" dialog).