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 90-s, but most software vendors got rid of them (MS Office "Options", Windows file properties, Total Commander "Options", Google Chrome and others). The main problem of this UI concept is inability to go through all pages (the tabs order is changing when user clicks the tab). If you've a property sheet with a lot of pages, we suggest to use a navigation list on left (as in MS Office "Options" dialog).