We have a use case where we have certain fixed date tasks and need to schedule predecessor tasks around these.

Predecessor tasks need to be completed with a lag before the fixed date. We should be able to schedule the start and end date for predecessor tasks as needed, and the changes should not change the fixed date task. Where a predecessor task is being scheduled so that it will be completed after the 'required' end date (fixed task date minus lag duration) this should be allowed but highlight this task as causing an issue to the completion of the fixed date task.

In other project management applications, this would be achieved through individual task constraints, but this doesn't appear to be possible within Zoho Projects? Is this the case, and has anyone figured out a workaround?