There is a bit of confusing nomenclature regarding this feature. Futhermore the feature has evolved over the years. I found this sentence in the R2018b documentation:: "[...], use code sections, also known as code cells or cell mode. " (I guess the word "cell" was mixed up with "cell" in cell array.)
Anyhow, the code of a script or function may be partitioned into sections with "%%". The section may be run one at the time. See Create and Run Sections in Code.
The toolstrip contains some tools to support this
R2018bIMO: code sections are useful when
- experimenting; searching for a code that solves the problem at hand
- developing scripts or functions, it devides the problem into small steps
However, I don't find it especially useful for debugging. Instead see Debug MATLAB Code Files
