Access Tables?
 

Under "Access to Items that are not common", "Rarity always reported" is "Uncommon, rare, or unique options will report an error message that they require the GM's permission. This can be suppressed by adding a choice to the Access table." Where can I find the Access table?

There's a section in campaign mode to adjust the player's options. I believe that's what this is referring to.

Left-Hand pop-out tab (in build mode) - very last item - "GM Approval". I'll add a note to improve our phrasing on that message - "Access [to uncommon/rare/unique items]" was our first idea for what to name that, but since "Access" is a PF2-only term, and other games have things you should only take with your GM's approval, we finally settled on "GM Approval".

You can also open the GM Approval list from the dropdown for the Access warning. (The same dropdown lets you suppress the warning.)