CurvaMask adds functionality similar to Quixel Dynamask to Substance Designer. WorldNormals allows you to create a directional mask from a worldspace normalmap and a given direction.
Download and extract the j_Masks directory in the zip file to your substance library directory. You can specify extra library directories in Designer. Tools->Preferences, Projects tab, scroll down to Library section, click on the + icon to add a library directory.
If you copied the substance files to your library they will show up in the Filters category with the Effects tag. Only use CurvaMask complex if your curvature map needs per resize level finetuning. See video below to quite a quick overview on how it works. Take note that, by default, Curvetype (Edges, cavities, both, curvature only) happens after resizes and blending. If you want you can do this before, this will change how each resize is blended together.
Combine the curvamask outputs with your own grunge and scratch maps to create some fancy effects.
If you copied the substance files to your library they will show up in the Filters category with the Normal map tag. Use the Normalized Input Vector node to specify the "light" direction since it auto normalizes the input. You can pick a colour from a worldspace normal map, or drag the sliders to change the direction.
Included with the zip file are some basic scratch generators. You can use the library quicksearch to find a bunch of scratch generators. Large scratches, Medium scratchs, Small scratchs (straight, v and z). Each scratch generator picks and places random scratch images.