Hello, 

We are trying to Implement a custom campaing element, SMS. 
We are following instructions from this website  : https://academy.creatio.com/docs/8.x/dev/development-on-creatio-platform/8.1/platform-customization/classic-ui/marketing-campaigns-basics/examples/implement-a-campaign-element#title-1455-3
We are facing a issue.
We created a test package named FZCreateCampaignElement which depends on our package FZCustomer360. Other package FZCustomer360 depends on : CrtBaseFinserv,
CrtBulkEmailInC360 ,CrtCampaignElements ,CrtCampaignInC360,CrtCampaignUtils,CrtContactToLeadInC360,CrtCustomer360App,CrtDigitalAdsInC360,CrtEngagementInC360,CrtEventInC360,CrtFinservSalesAndServiceApp,CrtLeadOppMgmtInC360,CrtOpportunityInC360,CrtSLAInC360,MarketingCampaign

Successfully we did this steps : 

1. Create a marketing campaign element
2. Create a property panel for the campaign element
3. Add the element to the element area of the Campaign Designer

At step 4 when (4. Create an executable element for the campaign element ) we created   executable element, we could not publish it since the class CampaignFlowElement could not be inherited.