The bulk edit option allows applying changes in a few Nodes at once. Both standard and custom Jira Issue Fields of the Node can be bulk changed.
How to Bulk edit the Hierarchy Nodes
Open the Create/ Edit Hierarchy screen
The Bulk Edit checkboxes are shown in each Node row and one above that lets to select all Hierarchy Nodes.
Click any checked Node summary
By default all checkboxes are checked, select only those you need to change for all Nodes
Click the Add button to apply bulk changes to selected Nodes
All fields will be rewritten the same way as the edited node. Empty fields will be filled with data and vice versa - if other Nodes contained data it may be cleared the same way as the main Node.