I don't think you can edit the workbench at all. You can use the filter on the activity list to show just actions taken.
I had a similar requirement, and the only way I found to do it quickly was in the email with the following script
(function runMailScript(/* GlideRecord */ current, /* TemplatePrinter */ template,
/* Optional EmailOutbound */ email, /* Optional GlideRecord */ email_action,
/* Optional GlideRecord */ event) {
var activities = current.incident_alert.source_incident.actions_taken.getJournalEntry(-1);
var firstUpdateContent = current.incident_alert.source_incident.description;
var firstUpdateTime = current.sys_created_on.getDisplayValue();
var firstUpdatePerson = current.incident_alert.opened_by.getDisplayValue();
var pattern2 = /^\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2}/;
var parsedTime = firstUpdateTime.replace(pattern2,"$1 - $2");
var activityArray = activities.split("\n\n");
template.print("<br/>");
for(var i = 0; i < activityArray.length; i++) {
var arrayEntryBefore = activityArray[i];
var pattern = /(^\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2} ... - \w*.\w*.)................(.*)/;
var parsedText = arrayEntryBefore.replace(pattern,"$1 - $2");
parsedText = parsedText.replace('\n','');
if(i===activityArray.length-1){
template.print(parsedText.trim());}
else{
template.print(parsedText.trim()+"<br/><br/>");}
}
template.print(firstUpdateTime + " - " + firstUpdatePerson + " - " + firstUpdateContent + "<br/><br/>");
})(current, template, email, email_action, event);
