We need a way to ask the user for input before proceeding with some actions, for example:

• The destination of a download
• Whether to continue to a capsule if it's a cross-domain certificate usage situation, required for #85
• Whether to navigate back or forward to a URL which resulted from submitting an input, required for #20
• Whether to continue to a capsule with an expired/unknown certificate, required for #16

qutebrowser's prompt mode, the obvious approach, has the following drawbacks:

• It's a new mode, but it would be weird to be switching tabs in normal mode and suddenly be stuck in a new mode because this one tab is requiring input.
• The keys required to answer need to be shown in the screen. Does it mean they are hardcoded?

Another option is to use the document itself. Have special links and inputs that, instead of navigating to a URL, perform an internal action within the browser. This doesn't require a new mode, and users can navigate these documents normally. Multi-step processes, like downloading a file, require more interaction and this solution may fall short. How do alert the user that the path doesn't exist? How do we autocomplete the path?