Adobe InDesign User Manual
Page 763

Note:
and applying the duplicated swatch to color objects that knock out. If you disable the overprint setting in the Preferences dialog box, all instances
of Black knock out (remove underlying inks).
It can be cheaper and easier to have the print shop overprint process black on the press.
1. Choose Edit > Preferences >Appearance Of Black (Windows) or InDesign > Preferences >Appearance Of Black (Mac OS).
2. Select or deselect Overprint [Black] Swatch at 100%.
Overprint [Black] Swatch at 100% does not affect tints of [Black], unnamed black colors, or objects that appear black because of their
transparency settings or styles. It affects only objects or text colored with the [Black] swatch.
Adobe also recommends
Change the appearance of CMYK black (Illustrator, InDesign)
758