Is it possible to add FOLLOW UNIT COMMAND to generals ?
If possible, please teach me how !

One way to achieve this is to make the unit use a weapon that gives 0.0001 damage on the unit you want it to follow.

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Wat. Elaborate?

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As for the OP...
No, you can't add a follow command, as far as I know, commands are hardcoded.

Ctrl-F does 'Formation,' basically if you have your units in a formation, Ctrl-F makes it so that they will try to maintain it as best as they could-- as with terrain and things in the way.

How they maintain this formation is that if you faster units up front, they will slow down for the slower units. Or if your faster units are at the back, they will slow down to maintain the distance from the slower vehicle.

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