Allow me to jump in briefly:
What are you trying to accomplish?
Even if you were able to hide those menu items (and of course, you can):
- If you click on "HikaShop" in the parent menu level, you'll get to see all the "hidden" submenu items again, plus some more, plus statistics.
- If you click on the remaining "Products" menu item, you'll get to see the HikaShop menu bar including ALL items possible, not only the "hidden" ones.
- Even if you managed to hide all this as well (which will be a lot of work), anyone accessing the backend including yourself will not see it anymore, means you'll be unable to change any setting other than related to "Products" unless going through major hassle to make things accessible again.
At this point a hint at the Business version, where you have an extensive ACL system allowing to specify who gets to see what. A few Euros more, but so much more convenient and effective.