I made a packaging design for a rectangular box and I'm trying to figure out how to indicate when a line is not simply FOLDED (as indicated with a dotted line) but CUT as a dotted line.
1When you say "CUT as a dotted line", are you referring to a perforation, where something can be detached?– DLevMar 6, 2017 at 17:24
Standard procedure in the packaging industry is to have a separate spot colour (and sometimes a separate layer too) for creases and cuts. So if you follow this rule, create a creases spot colour and a cuts spot colour and then a crease would be dashed line coloured as crease and the perforation would be dashed line coloured as cut. If necessary, you could have a third colour and separate layer for dimensions and notes.
However, this may all be besides the point because the usual process would be for the printer or finisher to provide a cutter guide and maybe even some samples based on your design brief. You should only be doing it if it's just for a mockup or an academic exercise.
If I understand your question, you're asking how to show that the item should be cut along a certain line?
I'd say the most common (and simplest) way of doing this is by placing scissors on the cut line, kind of like I did below: