You can access add-on services from Script Runner add-on. Followings are some example scripts. If you need a script, please let us know, it will be easier to write together. Please inspect JavaDoc of add-on's Java API to get an idea of what is possible.

Adding a New Single Select Attribute Value Programmatically

import com.deniz.jira.worklog.services.attr.AttrTypeService;
import com.deniz.jira.worklog.data.attr.AttrValueImp;
import com.onresolve.scriptrunner.runner.customisers.PluginModule;
import com.onresolve.scriptrunner.runner.customisers.WithPlugin;
 
@WithPlugin("com.deniz.jira.worklog")
@PluginModule
AttrTypeService attrTypeService;

//Set properties of attribute we want to add
AttrValueImp value = new AttrValueImp()
value.name = "My New Attribute"
value.description="Test Description"

//add attribute. Returned AttrValueImp has an "id" field which you can use for further method invocations. 
AttrValueImp newValue = attrTypeService.addAttrValueToAttrType(2, value)

Following script sets "Invoice Number" worklog attribute for every work logged in the system by listening "Work Logged on Issue" event.

Automatically Setting Worklog Attribute on New Worklogs

import com.deniz.jira.worklog.services.attr.AttrTypeService;
import com.deniz.jira.worklog.data.attr.*;
import com.onresolve.scriptrunner.runner.customisers.PluginModule;
import com.onresolve.scriptrunner.runner.customisers.WithPlugin;
import com.atlassian.jira.issue.*;
@WithPlugin("com.deniz.jira.worklog")
@PluginModule
AttrTypeService attrTypeService;
def invoiceNumberAttrType = attrTypeService.getAttrTypeWithName("Invoice Number").get();

def worklog = event.getWorklog(); //Every WorklogCreatedEvent has getWorklog() method.
Issue issue = worklog.getIssue();

//create a new worklog attribute value
AttrWorkLogImp attrWorkLogImp = new AttrWorkLogImp();
//set worklog id, issue id and project id
attrWorkLogImp.setWorkLogId(worklog.getId());
attrWorkLogImp.setProjectId(issue.getProjectId());
attrWorkLogImp.setIssueId(issue.getId());
//set type of the attribute and it's value
attrWorkLogImp.setAttrTypeId(invoiceNumberAttrType.getID());
attrWorkLogImp.setAttrValue(12345);

attrTypeService.addWorkLogAttribute(attrWorkLogImp); //set attribute on worklog

Following script finds text value of submitted single select worklog attribute for every work logged in the system by listening "Work Logged on Issue" event.

How to find text value of submitted worklog attribute

import com.deniz.jira.worklog.services.attr.AttrTypeService;
import com.deniz.jira.worklog.data.attr.*;
import com.onresolve.scriptrunner.runner.customisers.PluginModule;
import com.onresolve.scriptrunner.runner.customisers.WithPlugin;
import com.atlassian.jira.issue.*;
 
import org.apache.log4j.Logger
import org.apache.log4j.Level
  
def log = Logger.getLogger("com.acme.CreateSubtask")
log.setLevel(Level.DEBUG)


@WithPlugin("com.deniz.jira.worklog")
@PluginModule
AttrTypeService attrTypeService;

def invoiceNumberAttrType = attrTypeService.getAttrTypeWithName("Invoice Number").get(); //case sensitive
def workCodeAttrType = attrTypeService.getAttrTypeWithName("Type of Work").get(); 
def workCodeAttrTypeImp = attrTypeService.getAttrTypeImpWithId(workCodeAttrType.getID()).get()
 

def worklog = event.getWorklog();

log.debug("Script starting");

Thread.start{
    System.sleep(100);
    def existingAttributesList = attrTypeService.getWorkLogAttrList(worklog.getId())
	log.debug("existingAttributesList = ${existingAttributesList}")
	
    existingAttributesList.each { attr ->
        log.debug("attr.id:" + attr.id);
        log.debug("attr.type:" + attr.attrTypeId);
        log.debug("attr.value:" + attr.attrValue);
        log.debug("attr.valueFormatted:" + attr.attrValueFormatted);
    }
    
    def existingWorkCodeAttr = existingAttributesList.find {attr -> attr.attrTypeId == workCodeAttrType.getID()}
    log.debug("Value of Existing Work Code as Int:" + existingWorkCodeAttr.attrValue);
    def existingWorkCodeAttrDefinition = workCodeAttrTypeImp.attributeValues.find{ attrValue -> attrValue.id == Integer.valueOf(existingWorkCodeAttr.attrValue.toString())}
    log.debug("Value of Existing Work Code as Text:" + existingWorkCodeAttrDefinition.name)    
}

Browser not supported