In general, yes but there are limitations. Some of the plugins out there (like AdvancedCustomFields) save their data into the
wp_postmeta database table. From there you can use the saved data to include it into your snippets.
In versions lower than 2.10.0 this only works if the data is stored in plain text only. All you have to do is to select “Post meta field” for the field type and enter the name of the field into the textarea. The plugin will then try to load that data from the
wp_postmeta database table.
Since version 2.10.0 and up it’s also possible to target data that is stored as an array or an object. Read more on how to work with custom fields here.