@J.Hilk said in Set fixed margin/spacing/padding between Widgets/Layouts: @wrekler you have to set the margin and spacing of the QLayout item to 0 as well, not only in the StyleSheet. I believe those are 2 different pairs of shoes. @JonB said in Set fixed margin/spacing/padding between Widgets/Layouts: To clarify what @J-Hilk is saying (which I believe to be correct): a QLayout is not a QWidget and so cannot have its attributes affected via a stylesheet rule (sadly). That has to be done via explicit, back-end code. Here we go! That was the problem! Layout cannot be affected by a stylesheet file! Now I know how styling layout works! Thank!

@MCam Thank you, I was using plain adjustSize() that's why it didn't resize. Although there is problem that remains even when resizing both layouts : After unmaximising the window, adjustSize gives this result. I will mark the thread as solved because I can make the window to not be able to get maximized, but for completeness shake it would be nice if this result could be avoided. Either way, you saved my day and I thank you very much for that :)

I have posted suggestion about adding such positioner to QtQuick: https://bugreports.qt.io/browse/QTBUG-57549

@vladstelmahovsky Thanks. This solves the issue! Shame on me for not reading the documentation more thoroughly.