Thanks for your reaction, Rein
I was unaware that Joomshaper deliberately removed the back-end feature from their platform. In fact, I couldn't imagine such a thing, having built over 800 pages for my site using this feature (which seems elementary to me). This is also why I chose Joomshaper to build the site 3 years ago.
I would of course have appreciated a comment from the help desk like: "Be patient, this function has been removed from version 4, but it will probably return in the future". It would have saved me from installing each new version, in the hope that it would work, with each time having to return to the previous version. Obviously, it works, but doesn't the constant back and forth from version 4.x to 3.9 have consequences on the stability of the system...? We never know.
I saw the announcement of the return of the backend last week and I'm looking forward to seeing the results.
In the meantime, I'm keeping version 3.9, while taking into account the possibility of migrating to another pagebuilder system.
It would be nice from Joomshaper also to clarify if the new version with back-end will also work for Joomla pages as it does for version 3.9. Because I do not intend to develop my site with the "page" function of Joomshaper. Using SP Pagebuilder integrated with Joomla articles is an ideal situation for me.