Product: bryntum/gantt-trial@4.2.4
How to make particular task read only but its children tasks should be editable.
We don't support this field built-in, here is a feature request
https://github.com/bryntum/support/issues/665
But after you extended your data model (see an example how to extend model here https://bryntum.com/examples/gantt/advanced/ ), you can validate it using our preventable events, like
https://bryntum.com/docs/gantt/#Gantt/feature/TaskEdit#event-beforeTaskEdit
May be helpful to check validation strategies in this example for the Scheduler https://bryntum.com/examples/scheduler/validation/
All the best,
Alex