No, do not put toppings onto the bread before toasting. Any toppings that you put onto the bread may stick to the internal parts of the toaster. This can cause them to burn quickly and potentially cause a hazard.

If you have put toppings onto bread such as a spread, and have noticed residue inside the toaster, unplug the toaster and wait for it to cool, and scrub it off using a dry brush like tool.