I've found that if I first copy textures that FBX is referencing into /Textures project folder then after importing this FBX textures are automatically assigned to materials. But this requires putting textures of ALL models to import in single folder that leads to file name collisions. Is there any other place to put textures that Unity will automatically find them? I've tried /models/Textures when importing FBX into /models, /Textures/FBX_name without success.