I NEVER use the phone for convenience and security reasons (I'm probably too old to use the phone easily).
I haven't seen any good trading app that can be used from a phone or a smartphone.
I find it much clearer, more accessible and easier to use the laptop. in general I have always done any trading from a laptop
In rare cases when I am on the road and I need to close a trade, or perhaps I see a very good opportunity to enter a trade but I cannot use my laptop, then I will trade from my smartphone, but I agree that it is not very convenient, and is only suitable for some very simple operations.
It depends on what you want to do. To analyze charts or see things like finding rates, open interests and trade data, etc, then using a computer is better. But it comes to trade management (creating orders, closing orders, setting TPs and SLs, etc) then you need to be with your phone especially if you're going to be away from your computer, you'd need your phone to be able to manage those trades incase if goes against you and you have to close, adjust targets / stop losses.
Charting on a Mobile device is not the best experience that's why some very experienced traders even use multiple monitors.
Yes, for analysis, a smartphone is not the tool that will be your best assistant, but it can help out in some moments where using a laptop is impossible. Once I had to trade from a smartphone for several days in a row, because I was on the road most of the time and could not use anything else, and at the end of my trip I began to think that I was gradually starting to get used to it, that is, it is also possible, but it is much more difficult and requires more time for simple things that are done much easier and faster on a PC.