Is there any way we can populate dynamically dropdown list in RTE?

I tried to setup Dispatcher with docker in my local. All the steps are followed as mentioned in the document still i am getting below error 

i have a multilingual site in same domain, my requirement is to redirect different error pages for different site. 

I have similar requirement where i have to publish the page to preview url but the replication access is denied. So, it is executing another workflow i.e  request for activation to preview the page. I want to write a custom code to publish the page to preview. Anyone has any solution for this.