I do:
give @p diamond_sword{AttributeModifiers:[{Slot:"mainhand", AttributeName:"generic.attack_speed", Name:"generic.attack_speed", Amount:-2.2, Operation:0, UUID:[I;11168,11168,-11168,-11168]}]}
but it does 1 damage, can it save the base ones(damage and attack speed), without adding more modifiers? Or add a modifier with a new command
/data modify block -163 69 149 Items[].tag.AttributeModifiers[] merge value {Slot:"mainhand", AttributeName:"generic.attack_speed", Name:"generic.attack_speed",Amount:7,Operation:0,UUID:[I;11168,11168,-11168,-11168]}
but this removes the furst one.