Change the type, size, or style of swatches listed in the Multi-lister.
For example, if you have many shaders, texture, and lights, you may want to display only lights, or to display small swatches, or low-resolution swatches, to speed up the Multi-lister display.
See List menu in Render > Multi-lister
.
on the Multi-lister title bar, select Large Icons, Small Icons, or Text. 
The Multi-lister may not display very low-resolution swatches. In these cases, increase the swatch resolution.