There are occasions where you want to edit the previous sub. Lets consider the following example.
You added a sub event when a player was at the free-throw line. Following the first free throw more subs occur.
First the initial sub event was added:
Next a free-throw was added:
Now go to the sub for replacing an additional player:
If you try to save at this point with only replacing the player you get an error dialog.
Change the setting at the top of the screen to "Replace":
Now you get a confirmation dialog to let you know what is being replaced:
When you return to the game you see that you are still on the same place but the lineup has been corrected (The original sub event is still in the same place in the event log).
Note - if you replace the shooter in this manner it will throw a plus/minus report off by one as well as the lineup report. If you want those to be accurate then you need to add another sub which forces you to adjust the time down by 5 seconds (we are working on an alternative to that particular case).