How to pass execution context as a parameter from a button click in Dynamic CRM

For this we can user Ribbon Workbench and add Crm Parameter as our first parameter and pass Primary Control as a value. 

Please refer below image for details.

In JavaScript we can access the field or other values as:

function openDymoPrintAssistance(context)

{

    var formContext = context.getFormContext();

    var clinicappointmentId = formContext.data.entity.getId();

    clinicappointmentId = clinicappointmentId.substring(1, clinicappointmentId.length - 1);

If you are looking for how to create a perfect button, refer here

https://vjcity.blogspot.com/2019/06/how-to-create-custom-button-in-dynamic.html