No worries.
As I wrote above, I went all through the threads. The first occurrence of this topic was on 2016. The answer by developers was that they had planned to introduce a tool in the future. How much further ahead did they mean it to be?
Since there is a perspective tool for bitmap images in Affinity Photo, for what reasons not any correspondent tool was developed for vector curves for Affinity Designer in so many years? Is it too complicated? I don't know. You can stretch a vector curve as much as you want but if in Affinity Designer you convert art text into curves and try to combine all the letters into one single curve, even by subtracting them from a rectangle for instance, so as to have a masked lettering, every single letter keeps on behaving as an independent letter.
This is quite frustrating.
OK, I am not a professional graphic designer, I do things for myself and a few people. But I have been stuck for two days on a stupid banner.
I think that another thread on the same topic is just a good idea.