liveseopro

Custom Image Attributes is a lightweight WordPress plugin which allows you to add custom attributes to images on your website. You can add attributes to single images or all images.
You can use this plugin to add attributes to images as required by some other plugins, such as for lightbox, analytics and seo purposes. Add any attribute you like. Examples include;
data-lightbox=image-ad1 
title=demo 
alt=demo 
fetchpriority=high 
click-id=promo1 
or id, style, class, data, toggle & more
Free Features 
Add attributes to all images on your WordPress website. 
Add attributes to single images 
Remove attributes 
Disable native lazy loading for an individual image
Get Support 
Get limited support for this free plugin via the support tab.

Custom Image Attributes

Add custom image attributes to any image. Great for adding attributes to images for lightboxes, SEO, analytics & more.

Vadim Bogaiskov

Media file (image) does not contain field for title attribute, only for alt attribute.
Plugin add text into title attribute from alt attribute when image is inserted into post if title attribute is empty.
As alternative see plugin <a href="https://wordpress.org/plugins/restore-image-title" rel="ugc">‘Restore Image Title’</a> by Les Bessant. 
The ‘Restore Image Title’ inserted the post title into title attribute.

Title like Alt

Restores the title attribute from Alt attribute when images are inserted into posts

Custom Image Attributes vs Title like Alt