Currently, there is no way to achieve this directly; however, this can be done through a workaround. When recording new opportunities, create projects with the Marketing contract type for each opportunity. Assign the placeholder managers and clients to those projects. During the opportunity phase, record time and expenses to those projects. CORE automatically marks these entries as non-billable. After the opportunities are won, merge the Marketing type projects with the new projects to ensure you retain the time entries, expense entries, and any other information associated with it. Make sure that each opportunity has its own unique marketing project; reusing them might cause merging issues.