Hi,
You can set user defined defaults from Settings > Technical > Actions > User-defined Defaults.

This can also be set directly from an App/ model. For eg to set a default warehouse for sales  .. 

1. Open any sale order
2. Click on 'Open Developer Tools' icon (icon visible on the top right potion of menu, once the developer mode is enabled in settings)
3. Select 'Set Defaults'
4. You can define the default field & conditions if any and save.

Best regards,