How to establish multiple connections at the same time?

You can use the Generate Workspace option, which will automatically bring in the the readers and writers already connected.

That's great!

What is they all coming from multiple data sources?

@esalmagul​ you can also enable Feature Type Connections in View > Windows > Feature Type Connections to quickly connect different feature types and transformers. Hope this helps!

There is a quick trick that might be usefull also that I found on the FME training, this is the example:

This connects PublicArt to all of the neighborhood reader feature types by clicking on the red triangle going into PublicArt, holding down the CTRL key (⌘ or Shift on Mac), and clicking on each triangle coming out of the neighborhood feature types (Downtown, Mount Pleasant, Strathcona, Fairview, Kitsilano, and West End).