You do not have a false statement for the IF condition   Try... valueexpression=IF({numberOfChildren}=0,CONCAT({parentID},'-',{name},' - ',{plannedCompletionDate}),"")

You can sort of do this the other way around...  If you create a report of Reports, you can add a column for what Dashboards a particular report is on. Its a collections column. The script for the column is:   link.linkproperty.0.name=IDlink.linkproperty.0.valuefield=IDlink.linkproperty.0.valueforma...

Description - Add a new type of Custom Form for Reports.  Why is this feature important to you - This would allow the classification of reports and ability to more easily find reports and store metadata relevant to a specific company about the report How would you like the feature to work - Add new...

Description - Add ability to have / transfer ownership of reports Why is this feature important to you - The ownership of a report currently exists only by who entered a report. Often the report was written for a person/team but even when a person leaves the company they still are listed as the own...

Description - In the Set up of Request Queues, add a section to set permissions so that entered requests within either the Queue or the Topic can be automatically granted permissions Why is this feature important to you - Allows for more granular sharing or access of objects as they are created How...

Description - In a View enable the ability to Bulk Edit Sharing Permissions Why is this feature important to you - As Permissions are not always granted, it would be good to allow bulk edit of Permissions on objects such as Projects. Particularly to enable sharing to a Manager who may not be able t...

and you can do the valueexpression then just to add as much info about the document as you like as per my follow up example  

  Actually project is singular so...   listdelimiter=<hr>listmethod=nested(project).nested(documents).listsname=Project Docsstretch=0type=iteratevalueexpression=CONCAT({name}, " - " ,{lastUpdateDate})valueformat=HTML

nested(projects).nested(documents).lists will work for you

Have you thought about doing a report with collections and the column being assignments and then using an IF statement in the valueexpression to include the name as "" of the assignee if they have time but their name if the actual hours = 0