While working on a WordPress site, I observed the captions shown below images are left aligned.
There was a requirement from client to align the caption in centre.
I am sharing the script used for aligning the captions, you can use the existing ‘Additional CSS’ feature in the blocks or you can use a third party plugin for adding external css, also the default file editor.
/* align the caption on below the center-aligned images decryptweb-edit */
.wp-block-image figcaption { text-align: center; }
/* decyptweb-edit */
Hope this is helpful.