I misread the OP and provided an unuseful answer. Let me try again:
I think you're trying to solve a problem that does not exist. A project is not a process and is not exhibited using a process flow. At best, you would have a network diagram (which can look similar), often incorrectly referred to as a PERT chart, to pictorially exhibit how work might flow. But that is wholly different than a process flow.
In a project, it is generally understood that a project could be terminated at any stage and does not require any type of node or package that specifically calls for a controlled go or no go decision. The only caveat to that is if one purposely puts such a control in to have a go or no go decision, such as at a milestone to signify "going live" or a "gate" to proceed. Other than that, it is just a generally understood concept.
In a process flow, there is an inherent "stop" work at each process step that does not require a decision node to represent it. The verticle line on the right-hand side of a process step box means exit criteria that have to be met for the work to continue in the process. If the work has not met the established exit criteria, then the next process step cannot start. A specific decision node does not have to be indicated in the process flow as that would be redundant.
But the premise of your question depends on attempting to exhibit a project as a process and I think the premise is not valid on its face.