After Worklog Create/Update

You can execute a Groovy script just after usual handling of worklog create and update and perform additional logic.
Removing Each Worklog Entered in Child Issue of Epic from Remaining Estimate of The Epic

import com.atlassian.jira.component.ComponentAccessor;
import com.atlassian.jira.security.groups.GroupManager;
import com.atlassian.jira.issue.IssueInputParameters;
import com.atlassian.jira.bc.issue.IssueService;
import com.atlassian.jira.bc.issue.DefaultIssueService;
import com.atlassian.jira.bc.issue.worklog.WorklogInputParametersImpl.Builder;
import com.atlassian.jira.issue.IssueManager;
import com.atlassian.jira.issue.IssueInputParameters;
import com.atlassian.jira.security.*;
import org.slf4j.*;

Logger log = LoggerFactory.getLogger(com.deniz.jira.worklog.scripting.ScriptingService.class);

def issueManager = ComponentAccessor.getIssueManager();
def issueService = ComponentAccessor.getIssueService();
def authenticationContext = ComponentAccessor.getJiraAuthenticationContext();
def customFieldManager = ComponentAccessor.getCustomFieldManager();
def previousTimeSpent = 0;

if (update) {
  previousTimeSpent = previousWorklog.getTimeSpent();
}

def currentUser = authenticationContext.getLoggedInUser();
def issue=worklog.getIssue();
def epicLinkCf = customFieldManager.getCustomFieldObjectByName("Epic Link");
def epicIssue = issue.getCustomFieldValue(epicLinkCf);
def issueSpentTime=worklog.getTimeSpent();
def diff = issueSpentTime - previousTimeSpent;

if (epicIssue) {
    log.debug("Subtracting {} seconds from remaining estimate of epic {}", diff, epicIssue.getKey());
    def epicEstimate=epicIssue.getEstimate();
    Long epicEstimateUpdated=epicEstimate-diff;
    if (epicEstimateUpdated < 0) {
      epicEstimateUpdated = 0;
    }
    IssueInputParameters issueInputParameters = issueService.newIssueInputParameters();
    issueInputParameters.setRemainingEstimate((epicEstimateUpdated/60) + "m");
    IssueService.UpdateValidationResult updateValidationResult = issueService.validateUpdate(currentUser, epicIssue.getId(), issueInputParameters);
    if(updateValidationResult.isValid()) {
        issueService.update(currentUser, updateValidationResult);
    } else {
        log.error("!!!Error in Worklog Update Script:{}", getErrorCollection.getErrorCollection())
    }
}