Inconsistent string capitalization.

[talldan]

Describe the bug
I've noticed some inconsistent strings in the UI that could be improved.

The guide we're using is here - https://developer.wordpress.org/block-editor/contributors/document/copy-guide/#five-pay-attention-to-capitalization. It mentions that feature names are capitalized. It says 'feature labels' are sentence case. It doesn't show a feature name in a feature label, so this situation is unclear and open to interpretation.

In some places in the UI, features are capitalized:

• Welcome Guide (in the editor options menu)
• Block Manager (in the editor options menu)
• Reusable Block (the block's name. This also seems to be the only block suffixed 'Block', if that were dropped the use of 'Reusable block' elsewhere would seem to be ok)

In other places, they're sentence case (see almost everything in the editor options menu). Many of these seem as much 'features' as the Welcome Guide and Block Manager, especially the last four:

• Top toolbar
• Spotlight mode
• Fullscreen mode
• Visual editor
• Code editor

When used in sentences, feature names are handled inconsistently:

• Manage all reusable blocks
• Add to Reusable blocks
• Show More Settings

Then there are some that are easy fixes:

• Insert Before (should be 'Insert before')
• Insert After (should be 'Insert after')
• Move To (should be 'Move to')

To reproduce
Steps to reproduce the behavior:

1. Visit various parts of the UI

Expected behavior
Consistent capitalization.

[talldan]

Lots of these were changed in #18758, but I think that probably didn't go far enough, so it'd be good to iterate again.

[clucasrowlands]

Our team (Editorial) doesn't have a full picture of styling and capitalization in the UI (we only get glimpses into the interface from occasional Github copy review pings like this!), so I hesitate to offer specific feedback on what to do here. But I'll share general suggestions from our POV.

In general, we follow these guidelines for feature names/dashboard sections (title case) and feature labels (sentence case).

Specifically for different blocks, in editorial and marketing copy (e.g., en.blog announcements), we've been capping the name of the block but lowercasing "block" (e.g., Reusable block, Premium Content block).

"Visual editor" and "Code editor" are interesting — we've generally been going with the "block editor" everywhere (marketing, social, etc.), so wouldn't it make sense and be consistent to lowercase those, too? (I don't have an answer to that!)

"Top toolbar" and types of modes (spotlight, fullscreen, dark, etc.) seem broad and generic enough (like "dashboard") to lowercase as well -- but again, I'm not well-versed in all existing UI copy to make definitive suggestions.

[talldan]

Some of these were changed in #28486 to be more consistent:

• Insert Before (changed to 'Insert before')
• Insert After (changed to 'Insert after')
• Move To (changed to 'Move to')
• Show More Settings (change to 'Show more settings')

So I think that mainly leaves the Reusable Blocks copy as being inconsistent:

• Manage all reusable blocks
• Add to Reusable blocks

[ntsekouras]

Closing as the remaining Reusable related labels have been changed here: #29040, #27026