When opening a project and going to Tasks > Resource Utilization, it is not possible to do an inline edit for the ETC value after filtering by 'Assigned To'. However, if there is no filter applied to 'Assigned To', it is possible to inline edit the value for ETC.
When filtering by other attributes (for example, if you filter by Start or Finish date), the entries in the portlet are either shown or not shown. However, the 'Assigned To' filter also adjusts (recalculates) some values displayed, like the ETC.
If there is a task with three assignments, A, B, and C, each with 100 ETC, the Total ETC is 300. Filtering by 'Assigned To' "A" will adjust the ETC displayed to 100 (instead of the Total ETC of 300). Filtering by 'Assigned To' "A" and "B" (as it is a multi-valued lookup) will adjust the ETC to 200 for that task.
As the ETC is no longer the total ETC for the task (but a calculated sum of the ETC of the resources selected in the 'Assigned To' filter), adjusting the value is not permitted while there is an active filter in the 'Assigned To' attribute.
It is still possible to click on the task name to see the full list of assignments and adjust them individually, or if the adjustment needs to be applied to all of them, do not filter by 'Assigned To' so that the value displayed is the Total ETC, which will be editable.