Complex applications have a lot of components and controls and if you document them all with context-sensitive topics this means you need to create a lot of topics. This can be a very tedious task and it's also easy to make mistakes, because it means entering hundreds of context numbers and topic IDs that may not have very descriptive names.
Help+Manual can do all this work for you with the help of map files, which are simple text files containing lists of the topic IDs and help context numbers to be used for documenting the controls in the program. These files can be provided by the programmers (they can be generated by most modern programming languages). They have a standard format and syntax and Help+Manual can use them both to apply missing help context numbers to existing topics and to generate missing topics with the necessary IDs and help context numbers.