Below is a mockup of what I would like to be able to add some code somewhere so that a 'gift box' icon .png file gets inserted into the bottom toolbar ?(Similar to the 'Download" icon)? Here is an example:
You could make the gift icon an SVG and place it where you could place a logo in the Viewer Display on the left. You can add a link to it that points to the content you want to make downloadable. Here's more information: