Tool history
The Tool History lists all the tools you have selected since TVPaint has been opened. It is especially useful if you wish to reselect a previously used brush.
You can check the history by clicking on the icon.
The most recently used brush will be the one located on the upper-left-corner of the Tool History window.
The brush that has been used first will be located on the lower-right-corner of the Tool History window.

You can also clear the history by clicking on the skull icon, located at the bottom of the Tool History window.
danger
The Tool History will clear itself when closing TVPaint.