This is a third-party plugin used to create certificates. Wiki: https://docs.moodle.org/39/en/Custom_certificate_module
Adding a custom cert
Adding a custom certificate to a course works the same as adding any other module. In the target section of the course, the "Add an activity or resource" must be clicked. When the "Add an activity or resource" pop-up window is displayed, the tile named "Custom Certificate" must be selected.
This takes the admin to the page where the certificate instance will be created. A name and description have to be provided. It is also important to select settings in the "Options" section to determine how the certificate is made available.
When changes are saved, the certificate is generally created, but it needs to be edited to actually define what it will look like.
After clicking on the certificate on the course page, the admin will find on the next page an option called "Edit certificate", as shown.
On the editing page, the admin can define the certificate dimensions (length, width, margins) and also add various elements on the certificate's display (e.g. issue date, course name, student name etc.). Parameters are defined through text settings and elements are added through the "Add element" button (which directs to another setting page where that element is then defined). The hierarchy of elements is used to determine how the elements overlap; higher elements go in the background and lower elements go in the foreground. For example, in the image below, "Background image" is in the background of all the other elements. The hierarchy can be changed by using the arrow icons to move elements above or below each other.
Another setting below allows the admin to choose one from all available certificate templates, which are essentially presets. Clicking the "Load" button loads the selected template. Templates should already be defined to an extent (parameters and elements), and when a template is applied, parameters for the certificate instance can be modified and more elements can be added on top. Note: Template loading should be done before the certificate instance is defined, otherwise the loaded template will undo the parameters and elements selected for the instance.
Templates can be newly created or modified by going to the "Manage templates" link.
But the elements still need to be positioned properly on the certificate via the "Reposition elements" link before the changes are applied, in order to make the certificate look presentable.
The individual elements can be dragged and dropped via mouse click. Note that if a certain element is "missing" or "invisible", it is because the element hierarchy has not been set up correctly. For example, if "Background image" is the lowest element, it will cover all the text elements in the display.
When this repositioning is saved, the above display is what will show when the each enrolled course user downloads their certificate copy.
Certificate templates are added and modified via this linked page. Each template has settings similar to an actual certificate instance; parameters and elements are defined. When the template is applied to a certificate instance, the template's predefined settings can be used as a base to build the instance.
For example, the above template was loaded as a base for the example certificate in this article.