If you read the official Elsevier copyright and trademarks statement on the company webpage, the language seems to indicate that you need to to keep the ClinicalKey logos intact if you use the presentation maker features. However, the library has confirmed with the publisher that while you need to cite the source of your content, you do not need to preserve the trademarked logos indicating which publishing platform for the journal article, image, or ebook. Copyright protections and citation conventions dictate that you cite the source - not the platform for the source.
According to the ClinicalKey User Guide, Section 3.6 Citations:
"You need to cite all articles and books from ClinicalKey according to the American Medical Association Manual of Style, 10th Edition (http://www.amamanualofstyle.com).
The ClinicalKey corporate recommendation does not necessarily follow the citation style guidelines that you may need for your class assignments or for the publication of a manuscript. Since ClinicalKey contains different types of content you will need to note what type of material you are citing in order to follow the style rules for that type of resource.