Monomaker is a simple mono-merging and stereo-recentering utility plugin.

You can use the mono merge parameter to progressively merge your stereo audio channels into a single mono signal. Turning mono merge all the way up to 1 will make your sound completely mono. Turning mono merge all the way down to 0 will leave your audio unaffected.

You can then recenter your signal using the pan parameter. The panning is equal power (meaning that as you move further over to one channel, sound from the other channel is copied over to the first channel in order to keep the total volume consistent).

Also, in case it's useful, you can re-route the 2 input streams in a variety of ways by using the input selection parameter. "Left-right" means that everything is normal, "right-left" means that the left and right streams are swapped, "left-left" means that you lose the right stream and get the left stream copied to both inputs, and "right-right" means that you lose the left stream and get the right stream copied to both inputs.

Monomaker's signal path is input selection first, then mono merge, then pan.