Weld

Is it some commande that will weld all vertexes that lay in same position Without any selection, just push the button?

If you just want to weld overlapping vertex on a single object with a single button

Create a composite tool.


example:-

Go to "Composite tools > Create New"




The composite I would create is:-



What that tool(when executed) does is:-

Saves current selection mode.
Switches to vertex mode and selects all vertex.
Welds all vertex that are within 0.001 (you can change that to whatever distance is preferred)
Switches back to previous selection mode.

You can then add an hotkey to that composite tool "Edit > Customize > Tools > Composite Tools >"
Or
Add a user button to call that composite tool

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I have attached that composite tool, you can load into nvil via "Composite Tools > Import Composite Tool"

Works great thanks!