I don't know how it works with OSX, but with Windows, you have to make Hidden Items visible in the File Explorer view menu. If you use a lot of brush sets, then something I have been doing for years now, is to rename the sets so they list in alphabetical order with meaningful names. When using brush or pencil modes, you will need to set the opacity and flow in the options toolbar. Brushes are round with soft edges, pencils look more like drawn lines, and blocks are squares with hard edges. It is so easy to move presets between folders now, it makes sense to build yourself a favourites folder or two. Choose between brush, pencil, and block modes according to the effect you want. It took me longer than it should have to discover that simply holding down the Ctrl (Cmd) key when selecting one of those presets, will prevent it changing to another tool.

So you are using the brush tool and like the look of the presets I have highlighted, and you suddenly find yourself with the Smudge tool or Mixer brush. One of the things that has caused a lot of trouble is that CC2018 can now store tool presets inside the brush presets panel. At the bottom of the list choose 'legacy brushes' and click OK. Click on the upper right corner where the little cog with the small arrow is. You can reach it by choosing the brush/pencil option, then hover over the canvas and right click.

Sandra, the new brush set up is so confusing regards the different brush sets / folders, that what I have done is remove every single set from CC2018, and start again with the legacy sets. 1 Photoshop moved square brushes to a new section called: Legacy brushes.

Square brush in photoshop