By default, when you switch patches, the new patch is ready to play immediately. You can “defer” a patch change so that the patch change occurs after the last note of the previous patch has been released or sustained.
In the Attributes tab of the Patch Inspector, select the Defer Patch Change checkbox.
Note: Deferring patch change works in Perform mode but does not work when you are editing patches in Edit mode. You can defer incoming MIDI program changes and buttons mapped to actions but not defer patch changes made by clicking the Selector object or using the arrow keys.