The blocks of the Process Modeling Library are connected to each other via ports - the visual interface elements.
There are output and input ports in the Process Modeling Library blocks. You may only connect outputs to inputs, otherwise you will get a runtime error.
AnyLogic provides a set of options that allow you to customize the flowchart drawing process to your liking. These options are located in the Graphical editor page of AnyLogic preferences:
In Process Modeling Library it is possible to connect multiple output ports to one input port and vice versa, see the picture below.
In case multiple output ports are connected to one input port and more than one block wants to pass over an agent, the choice will be done in a "fair'' way: there is a kind of round-robin algorithm implemented in the input port.
If one output port is connected to several input ports, it will choose the "first in some internal order" port among those that are ready to accept the agent. More precisely, the output port will rely on the choice of AnyLogic engine among several simultaneous events. Fairness is not guaranteed in this case and such connection is therefore prohibited resulting in an error at model runtime. To have full control over the agent distribution, use the SelectOutput blocks or custom agent routing implemented via the Exit and the Enter blocks instead.