The usefulness and significance of the research plan for your work does not end once the Academic Council has approved your research plan. A new phase of implementing the plan begins once you start work on the research itself. It is a good idea to keep a note of what things work better for you, or allow you to take new directions in your research, when these are compared to what you originally wrote down in your plan.
An example: did the collaborator that you originally had in mind for a concert in the plan actually differ when it came to the performance night? What was the reason for the change? The reason should of course be noted down, but need only be included in the actual thesis if it actually relates to solving the research task (rather than some other matter, such as funding, personal chemistry, private matters, and so on).
In practice, the way that the plan relates to the research follows many different principles as the process unfolds. This ultimately depends upon the way you write.
Some examples of the writing style on the process: accustomed writers and copy editors, for instance, may be able to work directly on the manuscript of a thesis. A juggler of documents could be able to remember what was written where, and they may often keep a separate diary of the research process. Another way is to create new research plan files that are updates of the previous ones. If you do decide to take this last option, then do not make the mistake of deleting old versions though. Versions should be named clearly, for example ‘researchplan-nov2018’.
It is even possible that none of the text you have written when updating the plan or pondering on its development will actually end up in the final form of the thesis. It is nevertheless a very important means for getting your doctoral project into a written form.