Below are steps to hide the View All Site Content link in the Quick Launch Bar in a Content Editor Web Part (CEWP).
- Edit the page.
- Add CEWP to a Web Part Zone.
- Select Edit – Modify Shared Web Part
- Under Appearance, change title to Hide Quick Launch.
- Under Layout, check the Hidden option.
- Click the Source Editor button and add the following markup.
<style>
.ms-quicklaunchheader {
display:none;
}
</style>

