KewlSheet

Loopkut is a Blender add-on that previews inserted loop cuts at your mouse position in Edit Mode. It brings live snapping, multi-loop insertion, edge-flow smoothing, and a mesh bisect mode into a single modal tool.

Modifier Manager is a Blender add-on that adds utilities for the modifier stack, accessible from the right-click menu. It handles bulk selection, application, removal and copying of modifiers on objects in the current scene.

Target Weld is a Blender modeling add-on for merging vertices and edges interactively. You pick a source and a target in the 3D viewport, and it supports both vertex and edge merge modes.

Check Mesh is a real-time diagnostic overlay for Blender that highlights topology flaws inside the native Overlays menu. It catches N-gons, non-manifolds, complex poles, intersecting faces and more as you model.