Thank you for the reply, Thomaso. Space horisontally can be an option, when the sections to stretch are the same. But now I understand, that I should’ve uploaded a more complicated example, with different sections to stretch. Here is another example. Again, blue sections is what has to be stretched proportionally. Yellow sections are the sections of objects. And the orange sections shall stay unstretched. It’s like as if the blue sections were glued with their ends to the neighbouring sections:
And returning to Space horizontally option, in this case the notes are objects, I have the button “space horizontally”, but I couldn’t find the Alignment panel.