Making custom meta box required (with error message if not filled in) on Gutenberg

Related Posts:

1. Gutenberg add a custom metabox to default blocks
2. Add metabox to document tab in gutenberg
3. extend Meta Box / Document Panel
4. Unsaved changes in metabox inputs not detected in the block editor
5. How to validation for sanitize_URL?
6. Gutenberg add a custom metabox to default blocks
7. HTML for adding a meta box (basic text field) to page editor?
8. WordPress Blocks, setAttributes not saving
9. Individual Widgets per Page
10. Using TinyMce with textareas in meta boxes on custom post types
11. Tabindex on text input immediately after WordPress title input
12. How to add add_meta_box to specific Page Template?
13. Add custom fields within meta box class “on the fly”
14. Adding another state (spam, reject, approve) to wordpress comments?
15. Arrange custom fields with drag and drop?
16. Add multiple images to a page sidebar
17. getEntityRecord without knowing the post type
18. Populating meta box with select-list of existing posts, and assigning it to custom post types
19. Create meta boxes that don’t show in custom fields
20. How To Create a Metabox of HTML Content with Instructions For Editors When Editing a Post or Page?
21. How to load php file for specific page in admin?
22. How to set default metaboxes on user creation?
23. Metabox nonce PHP notice
24. TinyMCE in Custom Metabox not loaded after upgrading from WP 3.1.4 to WP 3.2
25. How to reload the role specific registration form on validation errors?
26. wp_editor in add_meta_boxes does not show gallery
27. How do I assign this filter to a variable? (Appending php & markup to the_content)
28. Create custom field key upon theme activation
29. Problem with adding exta field in metabox in custom post type
30. How do I add custom_meta_box_id’s value?
31. How to save multiple metaboxes?
32. add meta box using function.php
33. Metabox image upload and custom field
34. Transition from (classical) serialized custom meta field to (gutenberg) rest enabled meta
35. all tincymce’s switch when updating page after changing from html to text in custom metabox
36. How to construct multiple meta boxes
37. How to save a ToggleControl value in a meta field?
38. Force hide custom field metaboxes
39. How to Display Custom Meta Box only on Specific Page IDs
40. Custom Meta Box not Saving in Posts with Gutenberg Editor
41. Metabox will not save
42. How to update a meta field of type array in Gutenberg
43. Odd PHP Code To Display HTML Of Meta Box [closed]
44. custom field not saved
45. How to create a Custom Meta Box with Name/Value Admin User Input Fields?
46. Create Multiple File Upload Metabox in WordPress
47. Custom Metabox Not Saving
48. Better Method for Multiple Meta Boxes
49. Possible to add a meta field for css attribute to the editor Advanced panel?
50. Custom Fields box in the post editor: Replace textareas with input elements
51. Add new image block, set default class name and update it using Javascript
52. Get updated meta value after post update or published (custom post type) using hook
53. Button inside Custom Meta Box triggering the Update Button
54. custom-meta-box checkboxes from loop won’t save
55. Custom fields attached to a page template only show on edit screen when page is saved
56. I need a “Choose from existing content” popin
57. How can you include custom post meta in search without calling each key?
58. When creating a metabox do you have to create DB fields for the data?
59. Specific coditional usage [closed]
60. Set checkbox as checked by default in a metabox
61. Singleton Custom Field (Meta Box)
62. Warn user that data may be lost for custom pages
63. Move Title and the Content WYSIWYG editor position
64. How can I hide custom field from users used for caching response from external api?
65. How to disable Edit Post and Allow only Custom Field?
66. Displaying Meta-Box Data Properly
67. How to add fields in custom registration form, validate it and aave to db? [closed]
68. Is it preferable to use custom code to create metaboxes instead of plugins (such as ACF) and if so why? [closed]
69. How add multiple wp_editor_box to new post
70. Update post meta custom field using block editor
71. put saved metabox values back into fields and then display on the front end
72. HM CMB: Role Select
73. Custom metabox not working
74. Trying to implement AJAX into my admin pages. Am I improperly enqueue and localizing my scripts?
75. Meta Box Plugin Cloned Fields – Multiple Foreach values
76. How to Convert Custom Fields from Text to Array?
77. WP E-Commerce Custom Meta > Serialized array
78. Make separate text boxes for separate WordPress Custom Fields
79. show a specific metabox dependent on the page template
80. how to enable custom fields in the Gutenberg post editor
81. How to improve my non-unique metadata MySQL entries?
82. Adding text box with add_meta_box
83. Add forms dynamically in admin pages?
84. How can I ‘check’ the “custom fields” box from the Screen Options?
85. Can’t set custom meta fields for a post
86. get wordpress post loop by meta box date
87. Sub Field of File Field
88. If metabox fields has content display content
89. How to format the various types of custom fields?
90. Append custom field items to content from plugin
91. Display Data From This Custom Media Upload Meta Box?
92. When post is updated, custom metadata in text area field is overwritten
93. Call the latest posts from a custom field group to be displayed on front-page
94. My meta boxes update wp_postmeta of posts but not of pages. What is wrong with the code?
95. Can i categorise my meta box?
96. When editing a post with a custom meta box the values aren’t displaying correctly
97. Use Metabox to enter Post Title
98. Include custom fields into the content of a regular page
99. How to get the value of particular get $meta value in wordpress
100. Set post status to draft after validating post meta values in save_post hook