First of all, as of today (May 2016) I have not been able to find a direct way to move/duplicate photoshop brushes from one library to another. However, the hack that I am going to show you below works quite well
- Choose the brush that you want to copy
- Use it once (draw a line of whatever) so that it is registered as recently used brush
- Choose your destination brush library from your brush presets
- Select the brush from the recently use brush panel
- Create new brush – the brush will now be created in the current library
- Save the library using the save brush command from the drop down
OK folks. That is all there is to it.