Iframe tooltip to clarify system actions

[maufcost]

Hey everyone!

I had this idea while working on #1581 . This thread mainly focuses on the fact that setting an iframe's sizing option to be text-width or max-width, users won't be able to add a custom width to the iframe. To set custom width values, users need to choose the fixed sizing option for iframes.

I have been frustrated so many times that I am on a particular website, and something is disabled or blocked without it explaining why. Since we're blocking the width input according to some user actions, what do you think about this tooltip that lets users know why they can't add a custom width to their frames?