QuickNest Pro is a Premiere Pro extension from Vakago Tools built around un-nesting. Whether you're merging sequences or reverting a previously nested sequence, the extension aims to speed up that process rather than handling each nest by hand.
The tool covers both nesting and un-nesting. Alongside reversing nests, QuickNest Pro also lets you batch nest clips, an approach the developer notes is particularly useful when stabilizing clips that run at different framerates. The extension is compatible with Premiere Pro 15.0 and later versions, and it's listed as free here in the catalog.
The most recent release, version 1.0.4, fixed a potential issue that could occur when working with offline footage. For current licensing terms, downloads and further details, visit the Vakago Tools developer page.