Target Weld is a Blender modeling add-on that lets you interactively merge vertices or edges by picking a source and a target directly in the 3D viewport. It provides real-time visual feedback to highlight the components being merged. Accessible via the View3D Tools panel, it supports both vertex and edge merge modes with configurable behavior (press-only or click-drag).
The addon is free, you can support the author by buying their other addons from Superhive
typo fix
This extension does not require special permissions.
Useful addon, but there are several issues related to merging/collapse:
(Tested on blender 5.0.1)