When it has the box for the trailer under the 26000+ truck if it was no because it was over the 10k weight, then the arrow should go back to the class A part of the chart.

No need to go back at that point since there are only 1 way to get there on the flow chart: via a combination yes, then GVWR or 26,001 or more, then trailer 10,000 or less, then power unit GVWR 26,001 or more which requires a Class B.  If the trailer was over 10,000 you never would leave the Class A flow and end up in the Class B flow.  In reality, the only correction needed to minimize confusion is to remove the question since it is redundant since it was answered prior in the flow.

Class A CDL is only required for combinations that are 26,001 or more with trailers that are 10,001 or more.
Class B CDL is valid for power units with 26,001 or more and with or without trailers 10,000 or less
Class C is valid for power units 26,000 or less:
    1) without trailers    
    2) with trailers10,000 or less when GCWR is 26,001 or more, or
    3) with trailers 10,001 or more when GCWR is 26,000 or less