How to use TWO RUNES that requires same ITEM SLOT

Looking for some slot 2,4,6 will runes for my support monsters Song Destiny slow team RTA

I just realised that several of the weapons I found have no runeslots, even though they should AFAIK silver and veridum weapons should have

w96 slot How to use TWO RUNES that requires same ITEM SLOT at the SAME TIME in Season of

octopus treasure slot Weapons can have up to three rune slots at max upgrade level, and players can insert whichever runes they want to use as long as the rune