It may not always feel like it, but being delegated tasks from your manager is development for you.
Taking on tasks that are managerial in nature or a step up from your current role are all adding to and expanding your current skill set.
Willing taking on additional tasks also demonstrates your willingness to learn, prioritise tasks, effectively manage your time and put in extra effort when required.
To make the most out of doing extra tasks, make sure you keep a note of what you do, the skills involved and how well you completed it. This will all come in handy for your performance reviews and for adding to your cv or resume.