Adding classes in "Manual" classification method
Per this thread, it is not currently possible to modify the number of classes when using manual interval classification in graduated color symbology. The number of classes is there, but it is grayed out. There is a workaround, but it is tedious and destroys any values and symbology already set - flip to another method, add a class, flip back to manual, and reset your class breaks and symbology manually. That's not ideal, so I'm looking for the class number selector to be enabled here.
Hello,
As one comment mentioned in the previous thread, this is by design. Because with customized classes, it will be hard for us to decide where to add a new one or to remove which class. Any action might ruin existing manual classifications, so we grey out the classes control.
W have this more flexible function to update classes: if you right click on a row, you can choose to add a break above or below, and this will update the number of classes and don't need to switch to another method. Hope it will help.
Marking this as Already Offered per Zihan's response. As she showed, you can insert break above or insert break below. You can also switch to the histogram and manually insert breaks where you need:
