Firefox

The delete button, either it can be hidden in multiselect or the no of selected items can be updated when any item is deleted individually.

Example screenshots:

![screenshot_2](https://user-images.githubusercontent.com/36289013/129432070-258d47e1-5f62-4683-b3bb-8affddc0e1

fd = new FormData
fd.set('a', new Blob)
fd.get('a') === fd.get('a') // false in chromium - true in FF & Safari (don't have IE on Mac)

Looks like there is no test to cover this senario: https://github.com/web-platform-tests/wpt/blob/e45a9f9e65d039c76817ee2a6a1ef02c9311a1cb/xhr/formdata/set-blob.any.js

I think fd.get('a') === fd.get('a') should be true

Inside container tabs, the mode indicator sets a colored border using inline CSS with the !important tag: eg style="border: #af51f5 solid 1.5px !important".

This means you can't change this in theme files because the inline style always has the highest priority (At least I think, I'm a CSS noob). It could also theoretically be used for fingerprinting, but I doubt websites need to stoop tha