One approach I ahve used is to edit the Task Name by inserting "CANCELED - "
at the beginning. Then I change the Duration to 0d (since it is no longer
going to consume resources time).
There are 2 cautions though.
1. If there has been progress recorded against the task, do not change the
Duration to 0d; instead change the Work to equal the amount of work already
recorded against it).
2. You eventually want to show the task as complete, but you have to be
careful of when you mark it complete. If it has a predecessor task, mark it
complete only when the predecessor is complete so that the dates for any
successors remian accurate. Or you can remove any linkages to other tasks
so they are not affected and then mark ti complete.
Hope this helps.