[META][UX] Consistent "description" fields

[klonos]

...my OCDs are starting to kick in badly 😜

I would like to see as much consistency as possible across all description fields; especially the ones in the forms for adding things that reside under admin/structure. We currently have the following:

• "Add content type" form (multi-line, has description, but does not explain which tags are allowed):

  

• "Add custom block" form (single-line, no different label, has description, does not explain allowed html tags):

  

• "Add menu" form (multi-line, no description):

  

• "Add vocabulary" form (single-line, no description):

  

• "Add view" form (hidden via #states, single-line, no description):

  

  ...the same thing when editing an existing view, via the "View name and description" dialog (different field label, multi-line, now there is a description):

  

I have left some notable mentions aside...

• "Add menu item" form (multi-line but defaults to rows="1" 👍, has description (although not used in the admin UI), does not explain allowed html tags):

  

• "Add taxonomy term" form (rich text!! ...because it's not what it says it is):

  

[klonos]

...we should also be consistent about the allowed html tags for the description fields, and add that as a hint in the description text (see https://github.com/backdrop/backdrop-issues/issues/3885#issuecomment-504959009).

[stpaultim]

@klonos - I was going to put this in the OpenForce2022 project, but it occurs to me that some guidance on which type of description field is best would be very helpful to anyone working on this project.

Also, I wonder if they might want to fix 2-3 at a time, rather than trying to fix them all at once. How can we manage that?