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I'm trying to generate a Sequential Flow Chart (SFC) with the following input to make it easy for everyone:

% Example SFCs

begin{SFC}

    step{Step1}[Tran1] % Mandatory argument {<step text>} and optional transition [<transition text>]



    begin{Alternative}

        % First branch

        begin{Branch}[Alt 1]

            step{Step1-1}[Tran1-1]

        end{Branch}



        % Second branch

        begin{Branch}[Alt 2]

            step{Step1-2}[Tran1-2]

            begin{Alternative}

                begin{Branch}[Alt 2-1]

                    step{Step1-2-1}[Tran1-2-1]

                end{Branch}

                begin{Branch}[Alt 2-2]

                    step{Step1-2-2} % No transition condition

                    step{Step2-2-2}[Tran2-2-2]

                end{Branch}

                begin{Branch}[Alt 2-2]

                    step{Step1-2-3}[Tran1-2-3]

                    step{Other Example \ Test}[Test 123 \ This is a really long sentence]

                end{Branch}

            end{Alternative}

        end{Branch}



        % Third branch

        begin{Branch}[Alt 3]

           % This alternative route will be a skip

        end{Branch}

    end{Alternative}



    step{Step3}[Tran3]

end{SFC}

This is generating the following image now with my code:

However, I'm using a lot of nested tikzpictures. I've read that you're not supposed to do that. The tikzpictures are surrounded with a node, so I can create a path to the north or south of the tikzpicture. The following image displays the tikzpictures with a red dashed border:

The difficulty for me is the placing of the nodes and paths at the right spot, without knowing how many nodes of various sizes will follow, due to the input file. Each node(){begin{tikzpicture}end{tikzpicture} creates a group of nodes for me, to which I can create a path to the north or south. The node will grow in size according to the contents of the tikzpicture, which will push the other nodes around the group away, which is really convenient for me. Does anyone perhaps know better ways to do this? Due to the current nesting, I can't create paths between nodes that are not in the same tikzpicture. I'd like to be able to do that. Maybe someone knows a solution?

Maybe something with scopes might work. But I'd have to shift a scope below a node depending on the size of that the scope. I don't know whether this is possible. I'd also have to put scopes next to each other.