A URL can be pasted or written into the free text area of a Sets x Reps block section (as can a Personal Record) and it will be a 'live' hyperlink to wherever you wish.
We advise in the program notes a coach advises their clients to open the dropdown in order to see the URL the coach added for them
In the example below the URL takes clients to Concept 2 erg data workout screens:
This method adds URLs to the performance area for a client:
So upon a client clicking into a block section initially it's hidden to the client as it's closed by default:
until they open the drop down arrow next to the exercise: