The output consists of the category bar and the navigation bar.
How do I prevent the word repetition of bar in the English language?
Is it the following?
The output consists of the category and the navigation bar.
The original sentence is fine because you're introducing two items that are siblings. The "bar" is an important part of both items. An example would be like
"Here is a Phillips screwdriver and here is a Robertson screwdriver."
I would pluralize the word "bar" (since there are two of them) and say:
The output consists of the category and navigation bars.
Your version could be interpreted to mean that the output consists of a navigation bar and a category (not a category bar).