Please add such nodes as Transitions (Fork) and Transitions (Join) to the UML section of Palette
And these nodes must have proper behavior when I apply Swimlane Layout.
Swimlane layout is a general purpose algorithm that does not take any special flowchart meaning of symbols into account.
Regarding edge groups, either follow my advice in How to draw parallel process in UML notation in Swimlanes chart? or use Swimlane layout's automatic edge grouping feature (see tab "Edges" in the swimlane layout settings).