As it is now, the time entry import only allows to import time entries for a single, pre-selected project. Because time entries can only be imported for already existing issues (which in turn already belong to a project), by definition that pre-selected project is only relevant for time entries that are not attached to any issue.

The attached patch that was extracted from "Planio":https://plan.io/redmine-hosting allows to import time entries for issues across different projects. This is achieved simply by ignoring the user-selected project for those rows where an issue id is present, letting the existing logic in @TimeLogEntry#safe_attributes=@ determine the project id.

This is somewhat related to #25808.