Add multiple lookup account to opportunity

Hello !

I'm actually trying to add a multiselect into the opportunity creation form to link multiple account to my opportunity.

I have tried to add a lightning component to made that but i can't add successfuly the component into the "fields" of the opportunity form.

Is there a way to achieve that without a custom component ?

If not, did you guys have an example of how to add a custom component into form fields of an object ? (to use it in validation rules for example)

#Lightning Web Components #Aura Lightning Components 

Thanks for reading this and for any help that you can provide to me :)