No, it is not possible to apply markups on expenses on a project-by-project basis. The markup rate on expense categories is configured at the Account/Global level.
However, there is a workaround that you can employ to achieve project-specific markups for your expense categories. You can create project-specific expense categories that have their own designated markup rate. When creating expenses for a particular project, you can select the appropriate project-specific expense categories that carry the desired markup rate. This allows you to apply different markups for different projects.
The only drawback to using this approach is that when selecting expense categories for a project, you will see all the entries you have made at the account level in the expense category dropdown. This may result in a long list to choose from, but it enables you to assign the desired markup to expenses for each project.
By utilizing project-specific expense categories with predetermined markups, you can effectively achieve project-specific markups on expenses.