Metaparameters can be grouped, so that one metaparameter controls multiple targets. This allows you to create metaplugins in which a single host parameter has multiple effects. Each group consists of a master and one or more slaves. When a master is updated (manually or via MIDI), its slaves follow it. Only masters are exposed to the host, i.e. when the metaplugin is loaded in a host application, any slave metaparameters are hidden.
Group members can control targets in different plugins, or different types of targets, e.g. a mix of parameters and modulation properties. Group members can also have different ranges. By inverting one of the ranges, it's possible to create a metaparameter whose targets move in opposite directions, as in a crossfader.
Metaparameter groups have another use unrelated to metaplugins: they allow you to assign a single MIDI controller to multiple targets. The MIDI Setup dialog limits you to one target per controller, but metaparameter groups provide a way around this restriction. To assign a single MIDI controller to multiple targets, do the following:
To create a new group, right-click the metaparameter that should be the master, and select Group from the context menu. The Metaparam Group dialog is displayed. The dialog lists the names of every metaparameter that could potentially be a slave of this group. Each name has a checkbox next to it. Use the checkboxes to select which metaparameters should belong to this group, and then press OK to save your changes. Metaparameters that already belong to a different group aren't shown, because metaparameter groups can't be nested.
To edit an existing group, right-click any member of the group, and select Group from the context menu. Again, the Metaparam Group dialog is displayed. Check or uncheck group members as desired, and then press OK to save your changes.
To destroy an existing group, right-click any member of the group, and select Ungroup from the context menu.