Refactoring is a well-established software engineering technique aimed at improving code structure without altering its behavior. Each refactoring consists of a set of default modifications in a program. A thorough analysis of what code modifications compose a refactoring is a prerequisite to reap the benefits of this technique. However, there are at least two characteristics of code refactoring in real-life software projects that complicates a thorough code analysis. First, refactorings are often applied in a customized fashion, i.e., developers manually tailor a pre-defined set of code modifications (associated with a refactoring type) by adding or removing modifications to suit specific contexts. Second, refactorings are often intertwined with other tasks like adding features or fixing bugs, known as floss refactoring. Since refactoring modifications are often performed with other unrelated modifications in the same commit, distinguishing them is time-consuming and error-prone. While previous research has scrutinized these two challenging characteristics of code refactoring, specialized tool support for its thorough analysis is still limited. This thesis aimed at developing a comprehensive approach to assist code refactoring analysis in the presence of these two challenging characteristics. To this end, we first performed a study with developers to understand whether they would require specialized tool support for customized refactorings. Then, we developed two tools to assist developers in identifying refactoring-related modifications and distinguishing them from other unrelated modifications. The effectiveness of these tools was assessed through a user study with experienced developers.