Yes this is possible. Follow the steps below for providing multiple designation options in your donation form:
  1. Go to Fundraising > select Donation Management
  2. Click the All Donation Forms tab
  3. Find your form and click Edit
  4. Go to step 3. Design Donor Screen
  5. Click Edit next to Donation Form
  6. Add the data element titled “Designated Giving Donation Level” and click Save Order and Edit Selected
  7. In step 4. Designation Options Display, You can add additional designation dropdown lists by clicking Add a New Designation Option
  8. From here you can select a Single Drop-Down List and click Finish

This will add multiple selections in the drop-lists so that a donor can select multiple designations for their transaction.