Is there any way I can force Preview to always show the table of contents when opening a PDF? Most of the PDFs I use have a ToC, so this would save me the extra step from having to enable the ToC after opening the PDF.
This is currently not possible to be set as default in Preview. The closest you can get to this is Preferences → Opening for the first time: Always show sidebar. However, the sidebar that opens is the default thumbnail view, not the TOC.
You can provide feedback to Apple regarding this at the following page: