A distraction free editing mode would show you your document in full screen while hiding the menu bar, toolbars, status bar, etc. You would still be able to access these hidden GUI elements by, for example, moving your mouse pointer to the edge of the screen.
Would you want such a mode? Do you think TeXmacs would look more impressive in marketing videos/screenshots using such a mode?
You can actually use a trick by pressing Ctrl+F9, entering TeXmacs in presentation mode, no matter the document class you chose (article or beamer). You can from there adjust the zoom using the shortcut Ctrl+0, 8, 9.
I don’t it is the proper way to do it but it works so its better than nothing. Hope it suits you!
So some issues with presentation mode:
I use TeXmacs for taking notes with no page breaking and no margins. Unfortunately, this means that the lines are too wide in presentation mode. Maybe there should be a way to set margins just for presentation/focus mode?
For both marketing and editing purposes, presentation mode lacks the boxes that show document structure. These would actually be nice to have so people can see that this is a structured editor.
There is also a full-scree mode, which retains the visual cues, and the you remove the header bar (and even the status bar if you like). This provide such a mode. It would be maybe nice to have some UI popping up with useful commands, as replacement for the toolbar. Its appropriate design is however unclear to me.