Hi Andrei,

> Hallo Michael, is it possible to make isocurves to work on
> several faces simultaneously and follow one cuvrve?

It's difficult because there is no guarantee on any arbitrary joined set of surfaces that isocurves from each adjacent surface will make a closed loop like that. The U/V directions of each surface at joined edges are not necessarily aligned to one another.

What you show there looks like a planar section cut which you can do currently by drawing a line and using Construct > Curve > Project. Select the line, run Construct > Curve > Project, and then select your solid as the target object and you should get a result like that.

- Michael