I am trying to access the elements of Google Sheets sidebar I developed, using Chrome console. for example - getting width of an element:

$("#elemID").css("width");

where elemID is the dom element ID of a certain element in the page.

However, the element is not found and $("#elemID") returns null. This is happening for all sidebar elements, none of them is found in the console. see image.

Why is that? is there a way to achieve it?