In general the merge tasks function is a bit sloppy (user-oriented design would allow you to select the two [or more] tasks you want to merge, and be able to simply click the merge button).

However my main issue with the current system is that when you search for the task you want to merge with, the task you have actively selected also shows up. If the two tasks have the same name, and are the same task type and status, it's impossible to know which is the task you're intending to merge with, and which is the task you already have selected. Which just kinda wastes my time, y'know?