Copy steps/group of steps between Task Sequences
If I have to make a change to an existing Task Sequence (no matter if MDT or SCCM) I typically create a copy of the existing Task Sequence and apply the changes to this copy for further testing. This way you can easily test and improve it until everything is working as expected without having a negative effect on your working Task Sequences.
Now after you have verified that everything is working as expected, you need to redo all the changes applied so far to the original Task Sequence. The easiest way to get this done is by simply copying the steps you have added/changed from the Test Task Sequence to the original one.
In MDT this feature is available since MDT 2010. What some might not know is, that this does also work with SCCM Task Sequences. The only thing required is to keep both Task Sequences open while you are copying steps. It won’t work if one is closed already.