Don't put them in Allegorithmic path hierarchy folder, that path is only for program defaults. you should have a list of folders above that, something like "User\Documents\Substance Painter\shelf\" and in there there's a folder called "materials" - that's where you put custom or downloaded materials.
Maybe the folder where you are trying to import from contains accentuated letters. I couldn't import fbx files too because of this. To get around this issue, I made an import folder to inside UDK folder, and I save every fbx files to there now.
no thats not correct, whenever you press this button within a folder window you go ONE folder up, not back or anything else - its 1 folder up. Same for most Linux IDE's and I believe also in MacOs but I am not certain for the mac.