"Workflow engine" which works best in combination with uipath?

We are cleaningup our processes and are planning to automate some processes like searching date from SAP oder other Tools with a robot. But only robots do not solve all problemens. For example there are also requirements for an approval process other “workflow stuff.”
Does someone has experience with workflow tools? How they work togehter with uipath? Which limitation do these tools have

For example I found microsoft flow or signavio.

I think UiPath now has approval faeture built-in: