Mod managers are one of the intangible joys of modding Skyrim. If you're the kind of person who gets a thrill out of watching hundreds of disparate mods fall into place in the load order like Tetris blocks, mediating file conflicts, then breathing a sigh of relief as you start a new game of Skyrim without your PC blue-screening, then you'll love the Skyrim Modmapper.
This browser-based tool, created by dactyl, puts a grid overlay on a satellite-style map of Skyrim, colouring each cell somewhere on the spectrum between green and red depending on how many mods interact with that particular cell on the map. It claims to pull data "from almost every mod available on Nexus Mods to show which areas (cells) are being edited by the mods plugin."
By seeing which parts of the map are most affected by mods, Modmapper can help you manage file conflicts and get a feel for which areas and mods are most likely to cause problems for your modded Skyrim game. But even if you don't use it as a modding aid, it's just a very cool visualisation.
It's no surprise that many of the red areas on the map are around towns, but it's interesting to see that there are plenty of red cells over bodies of water— clearly, making smooth-flowing and realistically reflective water is a big priority for Skyrim modding community.
If you download the Vortex extension, you can right-click an individual mod from your list then click 'See on Modmapper' to see all the places on the map it affects. Crucially, you can import your own mod list and load order into Modmapper. Just drag-and-drop your Skyrim Data folder onto the web page, and watch your personalised mod heatmap generate before your eyes.
For now, Modmapper only covers the main worldspace, but dactyl is working to apply it to cities and interior areas next.