Creating own component templates (reusable elements)
Command-line is bridge between you and and actions inside Oxygen which you do by clicking. Clicking is not bad way, but when you need repeat same action with lot of clicks multiple times it can be inefficient way.
So how command-line solves that problem?
If you want add mutliple things you don't need type somehing, click, click, type again, click, type again.
You just need type what you want and command-line will translate to actions needed inside Oxygen to do all the things.
You don't think that you need that option?
Let say you have four unstyled buttons and want add three clasess to every.
Select first, go to command-line and write classes which you want add like .class1.class2.class3 if they exist you will get auto-complet suggestion so you can write typo-free and save some time. And after you have writen prest Enter. To apply it to multiple, just perform Shift-click on other buttons to repeat last command.
Now try just this common scenario perform by clicking via Interface.
Command-line uses commands which are calling native Oxygen functions to do certain things. So instead doing by clicking before typing, you can just write one special character which will indicate what to do.