Stobot,
In many ways alternative layouts were always possible, the new feature is there is now a standard switching mechaisium. Thus we can revert to the default easily, and we can deploy alternate layouts.
Please ask these question in another thread;
1. a top bar with a size (height) that I can adjust - am I right that we still can't modify this (without 3rd party plugins)? - No you can modify any part of tiddlywiki directly to achieve this.
2. a / the sidebar on the left - I still can't do that right? (without 3rd party plugins) - to me This is an example of a new layout, to get a left hand sidebar you may modify the $:/core/ui/PageTemplate, however a good design principal would be to add a Left hand side bar and Hide the Right hand one.
The following is my view point and others may add more, I have not yet implemented alternative layouts.
The nature of the layouts or page templates will be very dependant on the person making the layout. For those wishing to tweak the existing layout, replicating existing tiddlers then making changes may be the best way, if you stuff up access to your wiki returning to the previous layout may help you escape a mistake.
The tiddlers you may produce alternates for would include elements tagged with or using the tags below;
$:/tags/PageTemplate eg from $:/core/ui/PageTemplate especially $:/core/ui/PageTemplate/story
$:/tags/PageControls
$:/tags/ViewTemplate eg $:/core/ui/ViewTemplate
$:/tags/EditTemplate eg; $:/core/ui/EditTemplate
$:/tags/ViewToolbar
$:/tags/EditorToolbar
$:/tags/TopLeftBar
$:/tags/TopRightBar
$:/tags/SideBar
$:/tags/SideBarSegment see $:/core/ui/PageTemplate/sidebar
$:/tags/AboveStory
$:/tags/BelowStory
I recommend only changing what you need to achieve the result you want, this keeps alternative layouts as close to possible to core behaviours and will ensure maximum compatibility with other macros and plugins.
As an example I am keen to provide an alternate to the editTemplate that does not provide access to all fields and settings, but allows the user to edit content presented in a form a designer may want, eg update contact form. Reverting the layout to the standard only for designing. For example this alternative edit template may not use items tagged with $:/tags/EditorToolbar but An alternate toolbar so alternate buttons could be selected.
Regards
Tones