At the moment, in the chatbox of Pro Config apps you can only enter 1500 characters max. However, some LLMs like GPT4 allow 3000, and some like Claude Opus allow unlimited (?) at the cost of more battery.
My pro config bot has a proofreading mode that uses Claude Opus, but I can't post a text longer than 1500 characters in it which ruins the point of it... I know you can't anticipate in advance what task LLM the chat will use in pro config, so it's a difficult problem to solve, unless you outright remove the whole limit completely but I'm not sure if that will mess something up on some LLMs.