Groups can be connected by dragging an input/output Resource Type from one group onto another step/group in the design canvas. The layout of the design canvas will automatically change to reflect the new connections.
An important difference between group and step connections is that not all inputs/outputs in a group are available for connection by default. Some inputs/outputs from steps within a group may not be group input/outputs. Connecting groups/steps requires matching Resource Types between the inputs/outputs to be connected as described in connecting steps.
To make certain enclosed steps's inputs/outputs in a group are exported to the main groups inputs/outputs, open the group, select a Resource Type input/output on a step and select "Export to Enclosing Group". Resource Types exported to an enclosing group are denoted by a line connected the the Group Inputs/Outputs section the left/right sides of the design canvas.
To disconnect a group, right click on the connection between steps and select "Remove Connection".