In meta module pages the hamburger menu is not proper.

[smit08]

In meta module pages like meta handbook, meta trac, meta projects etc. The hamburger menu is not proper. It's in fixed position so floating all over the page. And due to that not able to view all the hamburger menu items.

[hilayt24]

The burger menu is now visible in the smaller screens previously it goes behind the main header.

[kajalgohel]

Hamburger menu start visible at 876px and below. I have added the css for 876px and below.

[dd32]

Page in question: ​https://make.wordpress.org/meta/handbook/

Instead of using px offsets though, we should use the headers CSS variables it offers to detect the offset (It updates them with the various header sizes)

[ryelle]

In 11573:

Make: Set mobile menu on top of the header.

Props smit08, kajalgohel, dd32.
Fixes #6096.

[ryelle]

In 11574:

Developer: Set mobile menu on top of the header.

Props kajalgohel.
See #6096.