Task report with filtering issues when task has multiple custom forms attached

Hi, 

I've created a report to show the custom forms attached to tasks. I have a new custom form that I need to attach to all existing tasks and I thought I could use the task report and filter for tasks missing a specific custom form and attach the form that way. I haven't had any success with the filters and it seems to be related to tasks having multiple custom forms, which is not working with filtering or grouping. 

When grouping, only the first custom form in the task shows. Is there any way to use text mode in a grouping to show all the attached custom forms as a string?

Is there a way to keep inline editing but show the task custom forms to be searchable in the report filter? Filtering for the form name missing didn't work, despite trying many combinations and types of category report field types. For reference, the text mode for Task-Category report field is shown below:

displayname=Custom Form Name
linkedname=direct
namekey=category.name
tile.name=component.objectcategories
valuefield=customFormsNames
valueformat=HTML
viewalias=category.name

I tried to find "customFormNames" in the API but didn't find it anywhere. I thought that may help.

Any ideas on this are appreciated. Thanks

Cathy