You have a list and a complex(its a relative term eh!) workflow with multiple approval paths where the approver needs to be able to input reasons for rejection/ approval. You have to do a little tiny add to the task list to enable the recording of comments and copying it back to a column in the list. Say for instance, your requirements are such that
1. Approver A approves a task, adds her/his comments
2. Task assigned to Approver B -> pass her/his comments and then upon approval
3. Task assigned to Approver A again for review-> review comments and then everyone is happy! Yay!
The first step you need to do to capture your Approver(s) Comments is to add Comments–existing site column to your Workflow’s Tasks List.
Then make sure it is the second or third in the ordering, just so it’ll show up without having to click More in the task item edit view. Once you have ‘Comments’ added to your workflow tasks list,
Steps required to capture comments of Approver of a task item
1. Create a workflow variable and capture the Task ID from Assign a task action in my example I called it taskID(I know, am the creative genius 😉 )
2. Create a string workflow variable and get the value of Comments field in Workflow Tasks list when its GUID =the captured Task ID
3. Update List Item if you wish to save the comments to the parent list as a column value and assign the column with the value of the string variable.
This step can be repeated with any number of Approvers/Assign a task actions. Mine works great with sequential approval workflow process.
Screen shot describes how you Set Workflow Variable with taskID.
Repeat the same for the rest of Assign a Task action, Set a string workflow variable with value of Comments from Workflow Tasks where GUID = taskID and then Update the parent list item with value of the string variable to the column in the parent list.
If all goes well for you, you should see also see something like this;
Huge shout out to https://community.nintex.com/message/5018#5018 that I used for reference.