Fumiki Takahashi

TAROSKY INC.

Hametuha INC.

This plugin adds a block to your block editor. 
This block changes its display depending on a current user’s capability.
<ul>
<li>You can set capability for block.</li>
<li>If a current user has a capability for the block, its content will be replaced.</li>
<li>Or else, block is displayed as log in link.</li>
<li>This block is an inner block, so you can nest any blocks inside it. Convert it to a reusable block for your productivity.</li>
</ul>
See screenshot for how block will be displayed.
This plugin use REST API to convert block content, so you can use it with cached WordPress. 
Even if you use CDN like <a href="https://aws.amazon.com/cloudfront/" rel="nofollow ugc">CloudFront</a> or <a href="https://www.cloudflare.com/" rel="nofollow ugc">Cloudflare</a>, this plugin displays proper contents for each users.
For performance enhancement, <a href="https://wordpress.org/plugins/cookie-tasting/" rel="ugc">Cookie Tasting</a> is recommended. 
It decrease server access including REST API by checking COOKIE value before accessing to server side script.

For Your Eyes Only

Add a restricted block for specified users.

Matthew Muro

Restrict Categories is a plugin that allows you to select which categories users can view, add, and edit in the Posts edit screen.
This plugin allows you to restrict access based on the user role AND username.

Restrict Categories

Restrict the categories that users can view, add, and edit in the admin panel.

For Your Eyes Only vs Restrict Categories