Is there a flowchart plugin (similar to VISO) available for InDesign?

Short answer is no, there's no specific add-in for this. Tools like RT's can do it, and you can use a second app and integrate the results.

My solution, when working for clients who didn't want to spare me a Visio license, was to create my own entire icon library and build flowcharts more or less manually, using ID's document grid. Since I've been doing it a long time, before/without dedicated apps, I find it easy. But it's not really a solution for efficient, frequent or often-modified charts.