Title of panel Categories & Tags is wrong when only one taxonomy is used

[benoitchantre]

Issue Overview

When a custom post type uses either Categories or Tags, the title of the panel is Categories & Tags.

Expected Behavior

The title of a panel should reflect its content.

Possible Solution

Use separated panels for each taxonomy or a neutral term like Taxonomies (or easier to understand ; maybe Classification).

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Tested with Gutenberg 2.0
Related to #2450.

[afercia]

Example screenshot: classic editor vs. Gutenberg (Jetpack's Portfolio "Project" Taxonomy):

As mentioned in #4934 there are also other labels provided by custom taxonomies the UI should probably use, for example the "add new", "parent", "choose", etc.

[jorgefilipecosta]

It looks like we have many possible ways to solve the issue:

1. Rename the top level panel to "Taxonomies".
2. Promote each taxonomy to be a top level panel (equal to the classic editor) so in the picture provided by @afercia we would not have "Categories & Tags" we would to top-level panels called "Project Types" and "Project Tags".
3. Use a more complex naming mechanism for categories & tags e.g: if categories and tags are the only taxonomies use categories &tags, if just category use category if tags use tags, if other taxonomy use "Taxonomies".

What are your thoughts on this?
cc: @afercia, @karmatosed, @mtias,

[afercia]

@jorgefilipecosta not sure. Personally, I don't like to have categories and tags in the same panel because when there are lots of categories (not so uncommon) I'm forced to scroll a lot to get to the tags form.

[karmatosed]

I would vote for:

Promote each taxonomy to be a top level panel (equal to the classic editor) so in the picture provided by @afercia we would not have "Categories & Tags" we would to top-level panels called "Project Types" and "Project Tags".

There is prior format for this in right now. Also having another level 'Taxonomies' seems to make not much sense to many.

[aduth]

Closed by #5183

[aduth]

Oops, for some reason I thought #5183 had already been merged. I believe the plan is for it to be merged shortly, otherwise this ought to be reopened.