Multiple default values Record Filter

Sorry to say but record filters accepts only one default option. Solution for it is to create custom sections

This feature already is part of a product enhancement request. But there is no date or version to it, so don't wait for it.

Unfortunately, setting multiple default values for a record user filter in Appian isn't currently possible. This functionality is a requested improvement, but it's not available yet.
As a workaround, you can consider using a saved user filter. Users can select their preferred options and save the filter for future use.