Sidehistorik
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Marketplace: https://marketplace.atlassian.com/plugins/com.fca.jira.plugins.workflowToolbox.workflow-toolbox/versions#b400
This has some very good field post-fuctions for handling lists and formatting text fields.
One of the best on paper (I have not worked with it) - but its not free, but its a afordable...
Scriptrunner
Marketplace: https://marketplace.atlassian.com/plugins/com.onresolve.jira.groovy.groovyrunner
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