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I'm sure you should contact the PCB house to specify blade angle etc. In DipTrace I would draw the lines and placed description texts on the Assembly layer, or some custom nonsignal layer, and then called the PCB house guys to make sure that they've understood my notes properly.
I think you should do that as well.
First make sure that your PCB fab is actually capable of V-grooves, and that they don't charge too much extra for it. If they do V-grooves then simply draw them as lines on a separate mechanical layer and export it as gerber layer "v-scores" or something similar. The PCB fab will know how to handle them.