The Muscle Save Weights dialog box includes options for saving and loading Muscle weights. The following settings and options are found in the Save Weights dialog box:
Used with the Mirror Position option. After a matching point is found, this does a Search/Replace on each original influence so that loaded weights can be applied onto a mirrored side. For example, if a Search/Replace is set to _L and _R and a point is found to be weighted to a muscle named MuscleBicep_L, when the weight is loaded it is instead applied to MuscleBicep_R.
When a weight file is saved, it also contains information on what original bones/muscles/capsules were used. Clicking this button re-selects the original influences based on the data in the file. This option works in conjunction with Search/Replace, so it can be used not only for reselecting all influences, but for selecting mirrored influences.
Loads the weights from the file onto the mesh that is deformed from the specified Muscle deformer node. This works for selected points. If no points are selected, all points on the object are automatically selected and loaded. When loading weights for mirroring it is important to only select the points on the side of the object you want to load so that the original side remains intact.