I would like to add an approval button on the list view of a record that allows

You could acheive this by creating a tempo report based on a portal task list (see the Portal to SAIL plugin). You can use SAIL expressions to build the list of tasks and therefore each one could have the approve/reject button. From the button click you could use the "Run Process Expression Function" plugn to call a process model which would then be able to send messages to your task processes and update them.

This is obviously quite an advanced approach using multiple plugins so use caution when considering your options i.e. is the Appian default behaviour really not an option?

You could acheive this by creating a tempo report based on a portal task list (see the Portal to SAIL plugin). You can use SAIL expressions to build the list of tasks and therefore each one could have the approve/reject button. From the button click you could use the "Run Process Expression Function" plugn to call a process model which would then be able to send messages to your task processes and update them.

This is obviously quite an advanced approach using multiple plugins so use caution when considering your options i.e. is the Appian default behaviour really not an option?