At this point the feature is mostly for developers or relatively technical users because there's no UI to load and install plugins and no repository to search for existing plugins. To try a plugin, you'd drop the JS file in the profile "plugins" directory as described here: https://joplinapp.org/plugins/ Later we can add a UI to do this as well as some way to enable/disable a plugin.
To make Joplin more extendable, a lot of code has been refactored or converted to TypeScript, and while all tests pass and I don't know of any bug, I wouldn't be surprised if I missed something so if you find any bug, please report it here.
Also if you try to create a plugin and run into any issue, please let me know. Also if a feature is missing to implement a plugin you have in mind, it shouldn't be too hard to add it to the plugin API.
In v1.1.4 if templates had not been set up there were only options to open the template folder or (IIRC) refresh. In 1.3.2 all options are present before any templates are set up, is this intended? There's no crashes and the dialogs seem to work, there's just nothing to show.
Also in 1.1.4 if the option to open the template folder was selected when there was not yet a template folder, one was created. With 1.3.2 Windows displays an error dialog stating that the folder cannot be found.
A new pre-release is now available. In order to support creating plugin custom command, the command system has been reworked and simplified. Normally it shouldn't have any visible effect, but under the hood it's much better and easier to maintain. As a bonus, these improvements mean we can now have a Command Palette - press Ctrl+Shift+P to invoke it and type the command.
By the way, for consistency I've now moved GotoAnything under Ctrl+P too and that means Print is now without a shortcut. I expect less and less people are printing documents, especially in this Covid time, and when they do it's not as often as when using GotoAnything or the Command Palette, so I feel it makes sense to remove Ctrl+P as a shortcut for Print. I'm only doing it now because of course you can restore this shortcut in the Keyboard Shortcut config.
There's two remaining issues left before the official 1.3 version is released:
Plugins: Adding support for "content scripts" to support adding Markdown-It or CodeMirror plugins for example.
I'm not sure if it's on purpose, but when I select an entry in the Command palette with the mouse, nothing happens. Using the keyboard (Enter) works. I use mostly the keyboard anyway, but it's something I've noticed.