edit the webassist/kfm/themes/webassist_v2/bb.css file.
change:
#template_sidebar{
position: fixed;
width: 200px;
height: auto;
right: auto;
bottom: 35px;
left: 0;
top: 66px;
background-color:#ccc;
border-right:1px solid #333;
}
to:
#template_sidebar{
position: fixed;
width: 200px;
height: auto;
right: auto;
bottom: 35px;
left: 0;
top: 66px;
background-color:#ccc;
border-right:1px solid #333;
overflow:scroll;
}