ID 457741 - Only one endGroup is created when adding Group knobs to the root node

Problem summary
Only one endGroup is created when adding Group knobs to the root node.

Customer reported version
nuke.12.1v2

Customer reported platform
10.15

Steps to reproduce

1) In Nuke on the root node (S in Node Graph), right-click the Properties bin and select 'Manage User Knobs'.
2) Create three Group knobs.
3) View any endGroup knobs.

Expected behavior
The Group knobs should each have an endGroup knob to control the grouping.

Actual behavior
Only one endGroup knob is created for manually created Groups in the root node.

Workaround
Manually add an endGroup knob to another node, and Pick... the 'endGroup' with enabling "clone using expression" to manually create it in the Root node as many times as necessary.

Reproduced by Support in:
Nuke 12.2v3 - Windows 10

Nuke 12.2v1 - Windows 10

Nuke 12.1v1 - Windows 10

Nuke 12.0v1 - Windows 10

Nuke 11.0v1 - Windows 10

Nuke 10.0v1 - Windows 10

Nuke 9.0v1 - Windows 10

Nuke 8.0v1 - Windows 10

Earliest version tested
Nuke 8.0v1 - This issue appears to be in all versions of the product

Tests

We can add acceptance tests to check the endGroup