Is your feature request related to a problem? Please describe.
(In classic) The trigger event>combat log>swing>missed is missing checkboxes for main/off hand. This checkbox does exist for event>combat log>swing>damage as seen below.

Describe the solution you'd like
Add a checkbox. The combat log event does contain this data.

Describe alternatives you've considered
This functionality can be implemented by parsing CLEU events, but that is a less user friendly solution