You can add check boxes for multi select fields:
To configure this go to:
Field manager ( either on global or event level)
select +Field to add a field.
give it a name and select Multi Select:
Select the desired Field category where you like the checkboxes to be available.
Select proceed.
Then select the component 'Checkboxes'
Add the desired fields and default field.
The fields will show up in the order you create them.
Remove the default empty value if this is not desired.
Select Proceed.
Your field should now be available as multi select check boxes.