Trump and his minions continue to say the she is incompetent but the facts do not support those views.
Kamala Harris was Attorney General for San Francisco for 7 years and Attorney General for California for 8 years. Both of those jobs require brains, talent and ability. She evidently did her job well as the was re-elected Attorney General for California in 2014.
I could not find any information about how many prosecutions were done while she was in either of those Jobs but I did find this comment from a person who worked in the AG's office in San Francisco
I live in SF, and I remember when she first ran for DA, being impressed by her front-line experience. The Alameda County DA's office was very highly regarded for professionalism, much more so than the SF DA's office, and that was where she'd spent her early career as a prosecutor. (I've never done criminal law myself, but I was on the civil side in the state AG's office, and I heard what the crime deputy AG's talked about.)
So, while I don't remember any specifics at all about her jury trials, when she ran for SF DA she stood out as an experienced professional prosecutor rather than a politician or opportunist. If anything, there was concern that she was too law-and-order for a progressive city.
While she was DA, my impression was that she took it seriously, and made some difficult calls even when they weren't popular.
When she was AG (I had left the office by then), my friends there found her to be pretty careful and controlling (not surprising since that's a huge office, and all the work is done in the name of the AG) but they didn't think she made decisions based on anything but the merits, or without careful review. (Definitely not a given, based on experience under prior AGs.) With some AGs, you'd wonder if they ever went to law school, but with Harris it was quite clear that the person running the office was a genuine lawyer.
Simple common sense would tell you that running the top legal position in a State for 15 years, requires knowledge, ability, and talent!
Oh and by the way, Trump is a convicted felon. Talk about irony of it all, with a prosecutor and a convicted felon running for president. You prefer the felon to be in charge?