Not a greatly known tip : City of Heroes - Submissions

2 identical enhancements in different slots on the same power can be combined when no longer needed instead of "trashing" the one you want to replace.

For example:
On brawl if you had 2 damage enchantments of 10 and you decided you want to replace one with accuracy you can combine the two 10's and make one 10+ instead of destroying the one 10 that you no longer needed.

On a side note.... a + next to the number means it is one level higher. If you have a 10+ it is the same as an 11.
A 10++ is the same as a 12.