Whenever you add a checklist item from the primary checklist to the current checklist the system should allow users to edit/add instructions of that instance of the checklist item inside of the details pane.
Typically, you'd have to write a check list item for every task that has a different set of instructions; however, the process should and can be simplified to allow users to add a checklist item, and edit the instructions after it has been manually added to the checklist.
This would allow users to create templates for specific tasks, and change the specific instructions for each manually created task. Attached is the location where the client would like to edit.
Sometimes the generalized task/title is the same; however, the instruction may be different.