Hello romatlo32,
There is no scheduled task setting for increasing the assigned Memory to a VM - only changing the reservations etc. as you have in your screenshot. The Memory cannot be increased in the state of the VM being powered-on due to Memory Hot Plug not being enabled as you understand.
The likely only way to achieve this would be via PowerCLI or some other timed script for editing the VMs settings while it is powered-off - if you are only planning on doing this for 1/few VM's then better to just do it manually (unless that is you also care about learning about how this can be orchestrated in which case research the automation processes).
Bob