Comps and MEMs

The COMP button, immediately above the T-Bar opens the Comp Bin, which provides powerful layer and effect control features.

Refer to section Comp Bin, but at this point it is important to distinguish them from Switcher MEMs.
Bumping the cursor at the left edge of the screen adjacent to the Switcher or an M/E reveals a MEM bin with features that are quite similar.
The main distinction between MEMs and Comps is that MEMs retain (and apply) all settings in the Switcher including source selection.

Viz Vectar Plus User Guide