Hello
Apologies for your inconvenience. As you know, SP Page Builder 4.0 has a completely new architecture and we can not add backend edit support to it. It is also easier for developers & users to manage using one editor only. But please note that we have decided to give regular updates to the 3.x series of our Page Builder as we have been for at least the next three years.
SP Page Builder 3.x series will continue to receive security patches, updates, and compatibility support for at least the next 3 years.
This is to ensure that you continue to have the greatest possible site-building experience as you have been. Meanwhile, we humbly request you to give SP Page Builder 4.0 a fair trial and see how you like it, gradually.