This is a custom Layout based on a predefined logic currently the RadDiagram does not support such custom Layout. There is a feature request to allow control over layouted elements logged in our system, you can track its progress and vote for its implementation in our feedback portal
. However you could give a try to one of our SDK samples
which implements a Layout based on a multiple roots just like you in your case. You could take advantage of the SDK and modify it to work for your scenario.
As for your question "Is it possible to place layers applying Layout() method, according to their connection?
". No currently there is no way to place layers which to be applied to the Layout.
I hope this information helps.
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