It is possible to use a URL that passes in an argument straight into a workflow. The workflow could then take this argument and use it in an activity
In Essentials Workflow Designer there is an arguments tab across the bottom of the screen. Create new arguments here. These are the variables that get populated with the value you assign them in the URL.
Here is the syntax of the URL query string fragment (what you tack on the end of a viewer URL):
&runWorkflow=<WORK FLOW ID>&argument1=FOO&argument2=BAR
You can then use the variables
argument2 in any workflow activity