Redesign editor header

[gordlin]

Description

When stuff starts happening, the editor's header starts getting rather bloated and can take up a lot of space.

Is your feature request related to a problem?

Both on desktop and on mobile, this can waste a lot of vertical space.

Proposed solution

Refactor so that the header uses less vertical space in general.

Alternatives considered

Some ideas:

• On small screen sizes, show only an icon in the buttons and use tooltips for the button texts
• "Double header": one line just for UUID/title, so it doesn't need to break line as often, and another for all the buttons
• Truncate title and UUID at one line, show tooltip if anything hidden
• Smaller text for title
• Move some of the buttons elsewhere

Related Issues

#503