This is an editor plugin for Godot Engine v4.X that allows custom snapping polygon vertices while editing tileset. It can help you until custom snapping appeared in new version
Simply download it from Godot Asset Library
Alternatively, download or clone this repository and copy the contents of the addons folder to your own project's addons folder. Then enable the plugin on the Project Settings.
MIT License. Copyright (c) 2023 Nikolay Lebedev aka nklbdev.