I looked into this a little while back RP.
Do you mean non-SAK folders?
If SAKs - I have imported dozens in the last few years - Including the OHO 130mm Wengers - which potentially could be confiscated as being nearly gravity opening (ie Spydie Flick). But I never had any problems. A couple of time packages have been opened by customs - but everything was always passed.
When I last checked the NSW law - It says collecting and displaying knives is OK - It's just carrying them, in public & without good cause, where you have a potetial problem. And of course knife shops (eg King of Knives) - Have some pretty gruesome fixed blades always on sale. Which, BTW, I never quite understood - ie you can buy/sell etc - But you can't carry!!
So if your folder is for collecting purposes, or a SAK, you should be OK