You need to you “Input Reference Set Selector” as the input widget. It will allow you select multiple data at one time.
You will need to use an iterator after retrieving a list of Tasks. Iterate over tasklist and create Detail_Checklist for each Task and associate it with the Task and Checklist.
Uncertain about your question, but I believe you’re asking how to assign multiple tasks at once?
The Cardinality in your Domain Model looks flipped.
You current have 1 Task can have multiple Detail_Checklist.
You want it the other way around. 1 Detail Checklist can have Multiple Tasks.
I’m uncertain about “Detail_Checklist” but based on your comment you’d probably want something like this (see below image)
1 Employee has 1 checklist, the checklist has multiple task.
You could add the attributes: Remarks and Status to the Task so they can be marked to done and commented on separately.