Hmmm, so is it possible to, let's say have an item called a thunder amulet. Then, when in battle, the player can use the thunder amulet and select from a list of pets that I've defined for the thunder amulet to be able to summon (in my case, all thunder type pets the player has in their party). I'm able to assign a thunder amulet to summon a single thunder type pet the player has, but not able to select all thunder type pets in their party.
It could be very well that you two are explaining it to me very clearly, but I just missed it in which case, I apologize! I'm fairly new to RPG Maker in general.
I guess there's some confusion in terminology here.
In RPG Maker, "Items" are usable items such as potions, quest items, ... Objects to equip on actors are called "weapons" or "armors".
I suggest to
1. Go into Plugin Manager and set "Summoner can summon X if…" to "It is a member of the Party and traits enable the Pet"
2. Go to database -> armors, and create your thunder amulet
3. Here, you can put either <Allow Summons: 1, 2, 3> or <Add Summons: 1, 2, 3> as already described in post 123.
Any actor wearing this amulet now can select available pets from their skill list.