I know what you mean. Thanks for trying.
All the slicers and charts are linked to pivot tables on another sheet. If I protect the pivot tables, the slicers and graphs cannot be changed indeed! I just hided the sheet with the pivot tables, so the chance will be little people "unhide" these and edit the pivot tables. I dont know another way...
The most important thing is that the graphs are protected as well. I cannot find the locked option if I right click on the slicers, but only if I right click on the graphs...