[a11y][Needs review][2.4.7 Focus Visible] Menu Bar not accessible using Tab key

[nkn2022]

Description

I am running an accessibility test suite with Notebook UI using the IBM Equal Access Accessibility Checker tool on Chrome browser. The results look good overall, only a few things are missing to reach a first formal level of compliance. So kindly help look into these.

Issues reported were violating WCAG 2.2 requirements.
Ref: https://www.ibm.com/able/requirements/checker-rule-sets

Full report (includes information on element locations where issue were found):
Accessibility_Report-7a73e10e-f8a4-4a06-a78d-5174a1309c5b.xlsx

Category: 2.4.7 Focus Visible

Ref: https://www.ibm.com/able/requirements/requirements/#2_4_7

Violation of Rule: element_tabbable_visible

List of issues with elements that violate this rule with a screenshots

Issue 1
Confirm the element should be tabbable and if so, it becomes visible when it has keyboard focus
Note: I see a lot of improvements have been made in this area with the latest version. Thanks for that 👍
But I see that this menu section is skipped when using keyboard Tab.
Element location:
<li class="lm-MenuBar-item" aria-disabled="false" aria-haspopup="true" role="menuitem" tabindex="0">
Screenshot:

Reproduce

• Install Chrome extension for IBM accessibility checker tool. Ref: https://www.ibm.com/able/toolkit/verify/automated
• Open Notebook UI on Chrome browser. Add some cells with code.
• Run the tool and we can see the above Violations reported.

Here is the screenshot of the UI scanned for the attached report:

Expected behavior

Menu is accessible using a keyboard Tab key
Reference on how to fix this issue can be found in these links:
Where possible, achieve the desired tab order by adjusting the DOM, rather than overriding the tabindex
Use standard HTML elements where possible, using CSS to alter appearance not behavior
Be familiar with established keyboard conventions
Implement keyboard operation for custom elements
Follow core considerations in reducing effort
Unit test - confirm component keyboard interaction