If you're done with an element, you can lock it by selecting it in the object explorer under the timeline and clicking the lock. This way, the element won't get in your way as you finish up other aspects of the wideo.
If you're working with a template and want to unlock everything to have full editing control, just select "unlock all" after you click the lock, and "lock all" when you're finished.
You can also hide or show elements by clicking the eye. Once you have locked or hided an object and want to unlock it or show it, you can select the object again from the Object Explorer.