EXS24 mkII allows you to use external applications to edit your sampler instruments.
Choose Options > Open in external Instrument Editor in the EXS24 mkII Parameter window.
Locate and select the instrument editor software.
Repeat step 1, but choose the Open in [name of external instrument editor] command. This is the same command as above, but it is automatically renamed after an external instrument editor is assigned.
Edit the instrument in the external instrument editor, then use the external instrument editor to send the instrument back to Logic Pro X.
Important: You need to save the edited instrument in Logic Pro X—not the external editor—to make any instrument changes permanent.
Hold down Option while choosing Options > Open in [name of external instrument editor].