In LRC, I have installed the plugins for Luminar Neo and Topaz Photo AI. There seem to be two ways to get to the plugins. One is File->Plugin Extras, the other is right clicking on the photo, the selecting "Edit In".
Question- why does Luminar Neo show up in both menu options, but Topaz is missing in the Right Click/Edit-In menu?
By @leer44346667
Because there's more than one way for a plugin author to tell Lightroom to send a file to their external application.
Luminar have written their plugin to use the File > Plugin menu, which triggers code inside the plugin to send the photo to the Luminar application. I would guess that the plugin installation or initialisation process also adds a file to LR's settings folder "External Editor Presets" which would make Lightroom call the Luminar application directly (ie not via the plugin).
Topaz must have chosen only the first, and it's hard to be sure why. It may be that they need to do something to the file before it hits their application, whereas Edit With operates more like dropping a file on their executable and wouldn't have that possibility. It might just be that they thought it would be confusing to have it in two places.