Menu specific variables

`$gbc-MenuWidget-margin-ratio`

Type: number

Default value: $theme-margin-ratio

Computed value: 0.6

`$gbc-MenuWidget-item-height-ratio`

Type: number

Default value: $theme-field-height-ratio

Computed value: 0.7

`$gbc-MenuWidget-tabbed-z-index`

Type: number

Default value: $z-index-Tabbed-Modal

Computed value: 57