Mitsubishi Electric MELSEC-Q Series Programming Manual page 67

Couplings must be provided when the parallel transition format is used. Program creation is impossible without couplings.
Ex.
Program without couplings (Cannot be designated)
4
As a rule, a waiting step must be created prior to the coupling. However, in cases such as the example below where each of
the parallel transition columns consist of only 1 step (program without a transition condition between the parallel transition
branch and the coupling), a waiting step is not required.
4 SFC PROGRAM CONFIGURATION
65
4.3 Transition