After rereading your posts, I realized that you didn't specify that this was for Social Security disability. If it's for private disability insurance, it's similar. I think that private disability insurers are better at evaluating professional job tasks than Social Security disability examiners are.
The type of forms that you're talking about are extremely difficult, in my opinion, to complete.
If you were able to do your job at one point and then became unable to do it, you sort of have to analyze what happened - what symptoms you started having and how they caused you to become unable to do your job consistently, reliably, and correctly. (Honestly, it takes the kind of mental effort that probably has become difficult just because of your illness.)
Back when I was having to fill out these types of forms, I often would get really frustrated because most doctors are not trained to know how to explain what needs to be explained. It's like you need a combination doctor/lawyer on your side.
I've been in a similar situation. I do feel like Social Security disability is much more oriented towards evaluating physical limitations than mental/intellectual ones.
One thing that Social Security does evaluate is if you're able to do a job consistently. If you found yourself doing okay for a couple of hours on some days then becoming unable to concentrate and starting to make errors, then that's important.
Also, if you showed a pattern of absenteeism, that's important. If you can get attendance records from your previous job, that would be helpful.
Do you think your former boss would write a letter discussing the problems that you had? I did not think to ask mine back when I was applying for SSDI. I think that it would have been helpful. If company rules prevent your boss from doing it, you might ask a former co-worker if there's one who knew what was going on with you.
Someone will probably correct me if I'm wrong about this, but when I was filling out the paperwork for SS disability, I also included ways in which my job affected my health negatively in addition to ways in which my health problems made it impossible to do my job properly.
I'm talking about things like when you end up doing nothing but working and sleeping and your social life disappears and then you end up with more emotional and mental health problems because of life balance or when your job and the mistakes you make there cause you so much stress that you start having emotional freak-outs at work. (SS may not care about that at all, but I did include it.)
(If this is for private disability insurance, they are probably wanting to know specifically how you can't perform your current job, so it's probably not as important to talk about how your job affects your health negatively.)
I think that your doctor is probably allowed to write a letter if he/she wants to, to go along with the forms provided by SS. If those forms don't even address the tasks that your job required of you, then I would just add relevant information on additional pages.
I don't think that restrictions necessarily mean that it would be dangerous for you to do something. It might be something that it's better for you not to do because it would aggravate your health conditions or something that you're not able to do because of your health conditions.
If you have a friend or relative or former co-worker who can do the actual filling-out of the forms for you, it can be good to let them do that. I know that may sound strange, but seriously, if you get approved for private disability benefits, they very likely are going to require more forms every six months to a year and they can, may, and have judged people negatively just because they were able to put in the intellectual effort to fill out their forms.
Okay, now I'm having flashbacks and grinding my teeth.