One frequent complaint about Burp is that it can easily accumulate a huge amount of data, in locations such as the proxy history. After lengthy usage, these repositories can become unwieldy, making it hard to find what you are looking for. Further, in noisy applications, such as those making frequent asynchronous Ajax requests, browsing a few pages can generate hundreds of individual requests, causing interesting items to get lost.
The new version of Burp uses display filters to address this problem. For example, at the top of the site map, there is a filter bar. Clicking on this shows a popup enabling you to configure exactly what content will be displayed within the map:
You can choose to display only requests with parameters, or which are in-scope for the current target (of which more shortly). You can filter by MIME type and HTTP status code. If you set a filter to hide some items, these are not deleted, only hidden, and will reappear if you unset the relevant filter. This means you can use the filter to help you systematically examine a complex site map to understand where different kinds of interesting content reside.
Sometimes, however, you accumulate data within Burp that you just don't need - for example, if you have browsed to off-target domains. In this situation, you can permanently delete the superfluous items using the context menu. For example, you can select multiple hosts or folders within the tree view and delete them altogether:
You can do the same thing by selecting single or multiple items in the tree view, proxy history, etc.