Thank you very much to deal with my problem, which may be much easier to solve than I think!
I am sorry to be too much enthusiastic and less detailed . Actually your screenshot is the best example. I could find easily the properties of polygon symbology were I can choose among the predefined fills:
But when the customization of the outline comes in I can't find similar built-in options, which are available for line features, like this:
What I could do is simply set line color and width OR compose myself from symbol layers like below, which sometimes requires too much efforts:
In many cases the built-in outline styles are good enough to use, or just need some minor adjustment.
I'm quite familiar with Desktop version but green rookie with Pro
Thank you in advance!