If you add YEP_AutoPassiveStates.js plugin, then you can do summoning and unsummoning with that plugin along with YEP_BuffStatesCore.js plugin:
Let's assume you have both plugins installed then you need to do the following steps:
#1 - Create an actor you wish to summon
#2 - Add this notetag to actor wich will be summoned
Code:
<Passive State: x> - keep in mind that "x", it will be needed later
#3 - Create a Common Event wich does Add a party member to team and place beneath it ControlVariables and select your unused game variable and set it value how long actor will remain in battle - for this particular solution, set it to 3
#4 - In skill wich does summoning place in effects that common event from step #3 (Should be like this:
https://prnt.sc/10ct9ox
#5 - Now, go to states section of database and create a dummy (empty) state and in notetag place this
Code:
<custom turn end effect>
var turns = $gameVariables.value(y)
turns -= 1
if (turns <= 0){
$gameParty.removeActor(z);
}
</custom turn end effect>
Now for the meaning of letters:
X - will be ID of state you place in actor's notetag -
https://prnt.sc/10ct3rf (in my case it's 99)
Common Event should look like that: -
https://prnt.sc/10ct7vu and state should be like this
https://prnt.sc/10ct657
Y - is ID of your game variable - I won't post a Screenshot, because at this point it should be clear how to use them (in this case it's ID 1)
Z - is ID of summoned actor from database (in this example it's 6)
Disclaimer:
This is only theoretical approach of summoning skill and I didn't test it, because right now I'm a little busy, but I'm sure someone will eventually correct any mistakes in my approach of summoning skill.
Good luck.
Edit: I made a mistake in skill's scope - It should be Battle Screen, not Menu Screen