Combinational loop

Port names are top-level I/O, so I assume you don't want that. Probably a pin name? Use the Name Finder and it will give you names that exist. You might want to do a false path -through the name, as -from/to must be endpoints, while I assume you're looking at a combinatorial node.

You're using IP that has never been analyzed in TimeQuest?

My guess is the reason there is no option to disable it is because it's normally not a problem. As FvM said, comb loops are in many designs and they go through. The tools probably already have too many options, so adding more for things that normally aren't a problem wouldn't make sense. (I think of the time there was a problem with Quartus synthesis running in the weeds and never finishing. After looking at the code, which was written by the user's internal high-level synthesis tool, there was a state-machine with 100,000 states. This was just not planned for by synthesis...)