The preset manager doesn't show an option to add Material preset to the default list

Steps to Repro:
1. Open attached or create new project
2. Project > right click > material
3. Select material and click slider/preset icon in the top right corner of transform component
4. Save preset
5. Edit > settings > preset manager
6. Click "+" to add default prest to list

Actual Result:
1. No option appears to add preset even though we have a material preset saved in assets

Expected Result:
1. It should show an option to add material preset to the list

Environment:
Windows and Mac

Occurring with:
2019.1.0a1, 2018.3.0b2, 2018.2.7f1, 2018.2.0f2

Note: preset manager was introduced in 2018.1 however its functionality is altogether not working for 2018.1.9f2

By Design:
Material presets are not supported as Default at the moment. The only supported default types for Presets are Importers, Monobehaviours and ScriptableObjects derived classes, which is not the case of Material.