STEPS TO REPRODUCE
- Go to Notifications Settings
- Click 'Add filter'
- Select a page from Location, an Action and an Event type
- On Channel, select only 'Alert'
- Click 'Save'
- Add another filter, but on Channel don't select anything (de-select Alert and Email)
The added filter takes into consideration the channel settings (displayed on Formats column), respectively 'Alert' in this case.
When nothing is selected on Channel, the 'Save' button is disabled.
The settings are not taken into consideration. Regardless if only 'Alert' is selected or no channel is selected (the 'Save' button is not disabled), the filter is created with both Formats, 'Alert' and 'Email'.