When should an author bring up disabilities and health issues that could affect their editing, schedule in the process? Maybe it's me. I feel like I am lying, if I pretend my health is perfect. I am mostly blind, and other health issues do slow me down. At what point in the query, acceptance process should I bring up my issues with an agent? I am able to work around them (sometimes slowly), and I don't want to bother an agent who doesn't want to deal with them. How can I recognize these?
You don't mention it in the query process. It's not about the book, and it's not a writing credential. You don't need to mention it at all as far as I'm concerned. If you feel like you need to be very upfront, you'd mention it when an agent calls to offer representation.
And any agent who rejects you simply cause you're not the Roadrunner is an idiot. You may quote that to them.
Writing well is a long game. If you're physically slow, chances are your brain isn't. More than half of a good novel is thinking about it. Thinking deeply takes time.
Editing schedules are entirely discretionary. If you need more time for things, you just get it put in the contract.
You have a sense of what your time line will be like. Several of my clients have been surprised by unexpected babies, illness, death and disability. We work around those too.
Quit worrying about why you won't succeed. Start planning for how to make sure you do.