Can you go online and fill out a request, or send email for begin excused and the reason ( health issues and a short bit about it)?

Some county and state do that, if you explain your limitations they usually are understanding.
You don't have to go into detail , just a basic idea of why you would have troubles sitting for x amount of time, need to move around for comfort, maintaining mental focus, travel to & from, etc..
They may require drs note as proof , so don't exaggerate anything.

Sitting / being at home is very different from sitting quietly in a court room..and having to focus on testimony..