Hey bro, how's it going?
I'll need some more clarification to answer your question. I'm not familiar with that VisuStella plugin, and I don't know exactly which elements it modifies to give you a prompt answer.
My plugin doesn't natively make significant changes to the RPG Maker's standard menu system; it only adds a button for the summon function. This button is directly inserted into the standard menu's options list and calls a script to open the window showing a player's summon list, so it would make sense that it doesn't interact with other modifiers in the same menu group or functions.
Could you record a video demonstrating this behavior or provide some screenshots so I can better understand what might be happening and try to find a solution?
Thank you very much for your interest and support!

