An implementation of the ExpAll functionality exists in Tim Core. Once a battle is over, if the owner of a particular Pokémon who was on the winning side in the battle holds a valid item in their inventory (or optionally just “yes” without a check), and said Pokémon would not have received experience due to Cobblemon’s default logic, the Pokémon is granted experience as though it had participated in the battle.
This can be toggled off in the config, to avoid collision with any other ExpAll logic present in other mods.
An item tag of tim_core:exp_all allows devs to add any items that should act as an ExpAll while in the player’s inventory. Make your own item tag JSON for it, add your own items.
The config option of forceExpAll ignores the check for an item in the player’s inventory if true. If you enable this, I advise turning off the ability to obtain ExpShares and any ExpAll items, as they would effectively be redundant.
The mod also offers the CHECK_EXP_ALL event so that devs can implement their own logic for determining if a given player should be considered to have an ExpAll after a battle victory.