Function header cell can be selected, but user can't set its properties in PropertiesPanel if the Function is the top level Expression of the BKM node. See below comparision of Function as the top level Expression. Once in decision node, then in BKM node.

Decision node

BKM node

Manual Acceptance test

• Select Expression Header cell of BKM node
• Change Properties via properties panel
• Try to clear BKM node definition, shouldn't be possible
• Build and Deploy decided not to check due to current issues on touched code
• Runtime decided not to check due to current issues on touched code