If you open JMRI and look in the roster directory, there should be a file for each locomotive .. if you keep your notes in the comments field, you can edit the xml file and copy the info to the new decoder file for that loco ..
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="/xml/XSLT/locomotive.xsl" type="text/xsl"?>
<locomotive-config xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="
http://jmri.org/xml/schema/locomotive-config.xsd">
<!--Written by JMRI version 5.0+Rc441642522 on Fri Jul 01 17:41:37 EDT 2022-->
<locomotive id="test" fileName="test.xml" roadNumber="" roadName="" mfg="" owner="" model="" dccAddress="3"
comment="this is were we keep the comments .. you can copy this to the new decoder file" developerID="-1" manufacturerID="129" productID="" maxSpeed="100" imageFilePath="" iconFilePath="" URL="" IsShuntingOn="">
<dateUpdated>2022-07-01T21:41:37.753+00:00</dateUpdated>
<decoder model="DN140" family="Basic FX" comment="" maxFnNum="28" />
<locoaddress>
<dcclocoaddress number="3" longaddress="no" />
<number>3</number>
<protocol>dcc_short</protocol>
</locoaddress>
<functionlabels />
<soundlabels />
<values>