Utilizes the native WordPress custom meta field. Both Gutenberg and Classic Editor supports Custom Fields.
Pick-n-Post Quote plugin allows you to display a static or featured quote for the current post in the sidebar area. Displaying quote author and source is optional. Supports multiple instances of widget with different styling if used on both sidebars.
If you wish to display random quote on a current post, a plugin “Quote Collection” by Srini G already exists for this purpose.
Add Custom Field
If you are using the Classic Editor:
If you are using the Gutenberg Editor:
Scroll down until you see the “Custom Fields” meta box. Click “Enter New” to add each custom field. Note that you only need to enter a field “key” once.
When there is an entry for the custom field, you can verify if the meta data value exists in wp_postmeta table in the database. For the custom field meta key to appear in the dropdown under “Add New Custom Field”, there must be at least a single value entered.
Pick another post. Since you already entered one entry for each custom field key, they will now appear in the Add New Custom Field “Select” dropdown. You just need to enter their texts in the “Value” area.