For a full list of compatible plugins, check out the Zotero Plugins Directory. To manage your plugins, simply go into your settings and they will be listed under the menu on the left side.
Sometimes you need to change the same error across multiple records, such as replacing "U.S. Environmental Protection Agency" with "EPA" across your entire library. You can do so using the Bulk Edit Script—no plugin necessary! Open the JavaScript editor that comes with Zotero (Tools > Developer) and use one of these prewritten scripts.
You can edit citation styles within Zotero using the built-in Zotero Style Editor (Tools > Developer > Style Editor). However, it requires understanding of Citation Style Language (CSL) markup. There are several tools that can help validate edited CSL styles:
You can find a full list of 10,000+ citation styles supported by Zotero in the Zotero Style Repository.