Cool news — like every other internet business in the 21st century, we allow you to use emoji in our product!
The best way to do something like this would be to replace the 'Min range label' and 'Max range label' with an emoji of your choice. .
These can be found when editing/creating any single- or multi-slider question.
If you're on a Mac you can do this just by hitting Command + Control + Spacebar.
On Windows this differs between models, but for Windows 10 you would hold down the Windows button + semi-colon.
If neither of those work, you should also be able to copy and paste something in from Google.