I'd like to customize the way the current (open) section is displayed in the toc. I've searched in this list but I didn't manage to find a solution. The available macros \pd@tocXXX (section 9.6 in the documentation) do not seem to permit this.
You mean that \pd@tocsection cannot know if it is the current one or not. You can, but you need a good look at the source. So, \pd@tocsection is used for sections, \pd@tochighlight for an open/active item, but irrespective whether it is a slide or a section. So, I understand that inside \pd@tochighlight, you want to know whether it is a section or not, so you can adjust the highlighting sections and slides. \@tempcntb is used to count the sections in the toc file. \c@pd@section is used to count the sections in the presentation. If they are equal, you have the active section. That's how \pd@pdcontentsline knows what to do. So use an \ifnum and that will help you. Good luck, best, -Hendri.