Multi-select, multi-checkbox, and similar custom field types can have multiple values. This makes conditioning a bit more tricky than standard single value fields.
The value returned for the custom field is a comma separated list of the values selected.
Be more careful when choice text overlaps
This is a simple example where choice text is distinct. You must be more careful with your condition logic if text for one entry is a subset of another entry.
In this case, the value of %custom-multi-checkbox% will be:
This example shows a condition to match anytime check1 has been selected. This means it will create when check1 has been selected in the original issue.
This example shows conditioning that matches when both check1 and check2 have been selected. Both must be selected in the original issue in order for the subtask to be created.
This example show conditioning that matches when either check1 or check2 have been selected.