When a registered absence conflicts with an assigned task for the resource(s), the following warning appears:

Here, you have two options:

From the conflict warning shown above, click the Cancel button:

In the above, you can change the date of the task or assign it to another resource(s). Then, click Save.

When a conflict appears and you wish to ignore it, simply click the Cancel button:

Related topic:

How to register team member's absence, holidays and public holidays

Absence in the Task Capacity

Absence in the Workload Sheet