Affected versions

• 89.0a1(2021-03-23); 88.0b1

Affected platforms

• Windows 10, macOS 10.15;

Steps to reproduce

1. Launch Firefox right click on the toolbar click on the Customize option;
2. Right click on the Customize tab;
3. Try to click on the Duplicate tab option;

Expected result

• for Customize tab the duplicate option should not be displayed, or if so it needs to be disabled;

Actual result

• duplicate tab option is enabled and clickable for this tab;
• reason why this will be set as S4 is that the duplication is simulated and tab "reopened", but not ideal;

Regression range

• First bad: 2017-09-02;
• Last good: 2017-09-01;
• Pushlog: URL;
• set as regression due to pushlog size, feel free to readjust if it's an intended implementation and swap this bug to/as an enhancement

Additional notes

• attached gif to best illustrate the issue;
• older builds, did not have the duplicate tab option at all.