I'm currently playing the blade singer build form Dnd Shorts , and im at the point where i can cast shadow blade and use booming blade while using it so need to roll a few extra d8S  i would like to know how to make a macro of this?

D&D Beyond doesn't do macros.

If you just want to have something you can click to roll, you can make a custom action for the damage.

It might not work perfectly, but in the action tab of your character sheet, you can click the "manage custom" to make a specific action pop up. Again far from perfect, but kinda possible?

Quote from UltraMonkeyX >>

It might not work perfectly, but in the action tab of your character sheet, you can click the "manage custom" to make a specific action pop up. Again far from perfect, but kinda possible?

 
I did cover this in the video I posted

Oh! My bad, I didn't watch the video because I post comments with reckless abandon lol.

Quote from UltraMonkeyX >>

Oh! My bad, I didn't watch the video because I post comments with reckless abandon lol.

 
Nah worries 🤣