Apps with 'Extensive customisability' feature

Cross-platform DAW for multitrack audio and MIDI recording, editing, mixing, mastering, scriptable automation, plugin support, and customizable workflow.

QTTabBar is an extension for Windows Explorer that brings tabbed browsing to Microsoft's file browser. It comes with a number of nifty features including a favorites function for launching folders and applications, groupings of folders that can be opened together, tooltip...

Nyxt is a new type of web browser for power users. It's built from the ground-up to be completely customizable. Out of the box Nyxt ships with tens of features that allow you to quickly analayze, navigate, and extract information from the Internet.

Doom is a configuration framework for GNU Emacs tailored for Emacs bankruptcy veterans who want less framework in their frameworks and the performance of a hand rolled config (or better). It can be a foundation for your own config or a resource for Emacs enthusiasts to learn...

Tribe is a white-label platform, empowering the new generation of online communities. It boosts users engagement and growth through widgets and integrations to existing stacks.