Nextflow allows to efficiently make complex pipelines. Some people understand things only visually, so it's important to make a good graphical representation. Way to do so in nextflow is by -with-dag command:
nextflow run <script-name> -with-dag flowchart.png
However, output looks bad and doesn't have any professional vibe to it:
I wonder if there are any ways to improve it, like getting source code and uploading on some different visualisation programms. Anything.
tl;dr: Use the -with-dag flag without a filename and use Graphviz to render the resulting dag.dot file.
Graphvis is a software package built specifically for visualizing these sorts of graphs. Nextflow's DAG visualization option will output a DOT format representation by default. Instead of specifying -with-dag flowchart.png use the naked flag -with-dag to emit dag.dot or specify the filename of your choice with the .dot extension. Rendering a dot file to a visualization is the subject of other questions and documentation.
