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Here's what an example tree would look like:
\begin{prooftree}
\def\fCenter{\mbox{\ $\Rightarrow$\ }}
\AxiomC{$\Gamma \Rightarrow \Delta, D$}
\AxiomC{$D,\Gamma' \Rightarrow \Delta'$}
\RightLabel{R}
\BinaryInf$\Gamma , \Gamma' \fCenter \Delta, \Delta'$
\end{prooftree}
If an inference is made from one premiss to a conclusion, it looks like this:
\begin{prooftree}
\def\fCenter{\mbox{\ $\Rightarrow$\ }}
\AxiomC{$D,\Gamma' \Rightarrow \Delta'$}
\RightLabel{R}
\UnaryInfC{$\Gamma \Rightarrow \Delta, D$}
\end{prooftree}
If height needs to be kept track of, here's how I did it:
\begin{prooftree}
\def\fCenter{\mbox{\ $\Rightarrow$\ }}
\AxiomC{$\vdash_{n+m}D,\Gamma' \Rightarrow \Delta'$}
\RightLabel{R}
\UnaryInfC{$\vdash_{n+m+1}\Gamma \Rightarrow \Delta, D$}
\end{prooftree}
An example of branching derivation with the heights kept at the left:
\begin{prooftree}
\def\fCenter{\mbox{\ $\Rightarrow$\ }}
\newcommand{\and}{\wedge}
\newcommand{\seq}{\Rightarrow}
\begin{comment}
Above is simply defined some custom commands for connectives
\end{comment}
\AxiomC{$init$}
\UnaryInfC{$\vdash_{n+m-1}A, B \seq A$}
\begin{comment}
This is the leftmost branch
\end{comment}
\AxiomC{$init$}
\UnaryInfC{$\vdash_{n+m-1}A, B \seq B$}
\begin{comment}
This is the rightmost branch
\end{comment}
\RightLabel{$R\and$}
\BinaryInfC{$\vdash_{n+m}A,B \seq A \and B$}
\RightLabel{$L\and$}
\UnaryInfC{$\vdash_{n+m+1}A \and B \seq A \and B$}
\end{prooftree}
\end{document}
