Logic Pro X Merge patch settings with the current patch
You can merge patch settings from another patch with the current patch. This has several uses: for example, you can merge effects with a patch while keeping the existing instrument, or conversely try out different instruments while preserving the existing effects setup.
The patch merging area contains buttons for four types of patch settings: MIDI effects, instruments, audio effects, and sends. By default, all four types are selected, in which case selecting a patch replaces the current patch. By deselecting some items, you can choose which patch settings are merged with the current patch. When you choose a different patch from the Library, only those settings corresponding to the selected buttons are changed, while other settings remain unaltered.
If you deselect the Sends button, the channel strip (or strips) in the patch can access the existing project auxes (or any auxes created by existing tracks/channel strips).
Open the patch merging area
Choose Enable Patch Merging from the Action pop-up menu at the bottom of the Library.
Choose which settings are not merged
Click one or more buttons to deselect those patch setting types.
Selected patch setting types are merged when you choose a different patch, while deselected types are kept unchanged.
Close the patch merging area
Click the close box at the upper-left corner of the patch merging area.
When the patch merging area is closed, choosing a patch from the Library replaces the current patch (equivalent to all buttons being selected).
When the main track of a summing stack is selected, patch merging is not available.