renp

Currently, when user navigates to WooCommerce > Orders and clicks on Order Notes icon, it opens the order itself. 
WooCommerce Order Notes Window plugin overrides this behaviour by opening modal window with 
the content of the Order Notes meta box.
Additionally, information about order note author is stored and displayed.
WooCommerce 2.0.x is required. The plugin is not compatible with WooCommerce 2.1 or newer.

WooCommerce Order Notes Window

Overrides the default functionality when clicking on Order notes button so that modal window with order notes is displayed instantly.

Yannick Lefebvre

The purpose of this plugin is to allow users to create one or more modal dialog(s) / pop-up window(s) that will appear when a user visits their site. The number of times that these can load is configurable. They can load content from external sites or custom HTML code into the dialog. This plugin can be used to invite people to register to a newsletter, respond to a survey, or simply welcome come to a site upon their first visit.
You can try it out in a temporary copy of WordPress <a href="https://demo.tastewp.com/modal-dialog" rel="nofollow ugc">here</a>.

Modal Dialog

The others either didn't work or caused massive JavaScript problems, breaking other plugins.

This plugin worked the best.

Worked better than the others

The purpose of this plugin is to allow users to create one or more modal dialog(s) / pop-up window(s) that will appear when a user visits their site.

WooCommerce Order Notes Window vs Modal Dialog