Help: Trying to create a spawn elytra plugin!

I am trying to make a mod that gives you an elytra when you execute a command and tkes it away when you land! but I dont know how to specify the player that executed the command in the landing procedure as the target entity! maybe store the value somewhere else or is it possible to use the entity falls trigger? everything can be seen in the pictures in the drive link! tanks for helping

https://drive.google.com/drive/folders/1ItKh9MNlegXuLEh8cnH9N1E_Fkqx05B…