Plugins are used to add features to financial software such as more concise reporting, the ability to import data from other financial software, enhanced budgeting features, specialized account views, or other features.
Since plugins are separate from the software they work with, they are downloaded and installed after the financial software is installed. It's usually not difficult to use plugins, but be sure to refer to the documentation for your financial software before you attempt to work with one or more.
Check the website for your software for a list of currently supported plugins, since it is possible for the financial software to be updated while a plugin is not. In this case, the features added by the plugin will usually just stop working, but it is possible for an outdated plugin to cause unexpected results across the software.

