WordPress change the editor, Gutenberg is the current next way to edit content. But some people use Shortcodes or/and the Classic editor also inside the block editor. So the plugin is old, but helpful, maybe needs more feature. The current version has some issues for Ex/import and should be fixed. The code is public on GitHub (https://github.com/bueltge/addquicktag) and here on wp.org, so perhaps the community will contribute in development and support.
@bueltge Hm, that sounds positive and negative at the same time. There are countless users who still use the classic editor and want to continue to use it, because their system and the entire website is built that way. I also use the Classic Editor plugin myself and know enough who use it. Gutenberg is terrible, in my opinion. Maybe nice for a small website where you change an image or text every now and then. But if you maintain a professional website with many posts, it sucks. I also don’t know how to incorporate the many “Quicktags” created so that I could use them without the AddQuicktag plugin. Much depends on the use of these Quicktags in my daily work.