Just a simple Userscript that uses event delegation/bubbling to automatically track usage and display the next reset.
It has separate counters/timers for GPT-4 and Custom GPTs, since those have different caps (and not necessairly the same reset times).
You can hover over the counters and buttons will appear to manually control the values. You can also edit the reset times.
You can also find it on greasyfork: https://greasyfork.org/en/scripts/482585-chatgpt-gpt-4-counters
If you have any bug reports or suggestions, make them here or hit me up on discord (lugia19)