Detail
Detail
The dropdown is currently structured in such a way that the expanding part (the list with the items) is located in the HTML structure next to the button of the dropdown.
This works well in principle, but has the disadvantage that the list can disappear under other elements if these or one of their parent elements has a set higher z-index than an ancestor/parent of the dropdown.
Specifically, this problem occurs in tables, where the table headers have an assigned z-index that is higher than the z-index of the table body. A dropdown that is now in the body, opens towards the header and overlaps with it, is therefore behind the header and is thus covered by it.
To prevent this behavior and allow the dropdown to be displayed above all other elements, the dropdown should now be reworked so that the list of items opens at the very outside of the DOM tree.
Test
Open table with dropdowns, position/change window so that dropdown opens to the top. The dropdown list now overlaps with the table header and should be displayed above it.
Otherwise, the functionality of the dropdown should have remained the same. (see #27330)