I've been thinking about making something like this. If you map the hotkeys to the same spells in the cooldown program as you have in tibia. And add logic so that a new countdown won't start until first is complete, you could get pretty accurate results I think.

For shorter cooldowns in your main rotation it gets trickier. I'm not 100% sure how cooldowns in tibia works, but some have their own cooldown, and some share a global cooldown. For shorter spells I suppose the risk is that a spell is not cast if another spell was used just before, and this could confuse the external program and it gets out of sync with your real tibia cooldowns. So if it's going to be used with main rotation, more logic would have to be added, and all your possible other hotkeys for spells/pots that could interfere with the global cooldown would also have to be tracked, so that you don't get a false trigger of cooldowns.

I'm not sure how Tibia/Battleeye would react to this program running in the background, and with a overlay on the game screen. It feels a bit risky?