Hide sketches one drawing view only

Once the drawing views have been created there is no link between the visibility of the sketches in the drawing and part.  A macro would be the fastest option here, but you can also use the filter at the top of the Drawing tree to filter "Sketch" and then select all the sketches you do not want to see and hide them.

The last option would be to hide the sketches before hand and then create the drawing.

If you need sketches to be shown in the drawing e.g. for the flat pattern and have made some other views that sketches appear in. It is not enough to go the the part/assembly and hide them there. You need to hide them manually in the drawing or rebuild in the drawing and make the views again.

Honestly, I would say that the  easiest way would be to make sure that your sketches are hidden at the part level, then come back to the drawing and show the bend lines in the flat pattern view.

Alternatively, you can not worry about sketches at the part level, and hid sketches from the tree in the drawing.

I realize this will be hard if you have hundreds of sketches, but I don't know of a way to turn off sketches on a view by view basis.  Only for the entire drawing or not.

In your Drawing, select the Bend lines.  Then, while they're selected, use the Convert Entities function (on the Sketch tab of the Command Manager, or Tools > Sketch Tools > Convert Entities) to place sketched lines coincident with them.  Now hide the sketches and the new lines will remain.  You may need to use Layers or the Line Format toolbar to get the desired appearance on them.