Dear aspirant,
Hope you are doing well. As per your query it will best if you can do JOSAA choice filling in a desktop as you will be able to see all the options at once which will be much easier for you than using a mobile phone. Please click on the link below for more information and updates. Hope you find this helpful.
https://engineering.careers360.com/articles/josaa-registration-and-choice-filling
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile