Here is a PG to place yellow box at vertex points https://playground.babylonjs.com/#I0TSSC#7
Note Lines
17 ---- Cat has been loaded with non- zero position and has been scaled, so any positioning of a yellow box will need to take this into account. Remember that positions are stored as with zero origin and a unit scaling.
47 ----- stored positions transformed before use to position yellow box.
Note as you drag the yellow box the actual change in a vertex position may need scaling.