Could a slightly bent rear mech cable be the cause of poor shifting? I have trouble indexing my SRAM Apex 1x drivetrain. If I get it to shift correctly at one end of the cassette, it doesn't shift so well at the other end.
Sometimes I have to click multiple times at the DoubleTap shifter to make the rear mech move enough for the chain to jump to the next sprocket.

I have tried the usual, first of all the chain tension barrel adjuster at the rear of the mech. Also, I have tried removing the cable from the mech, changing the tension.
And fiddling with the B and limit screws. To no avail.

For context, the drivetrain has recently been moved from a few years old bike to a brand new frame by a seasoned bike mechanic.

Could a slightly bent rear mech cable under the BB be the cause of the poor shifting (see photo)?

And if so, can something be done about it - other than replacing the cable?
No, the 'bent cable' is not causing the problem.

As soon as the shifter pulls the cable the tension of the derailleur springs will straighten it out. It may be slightly bent when first installed but should straighten out in a short time.

The excessive slack you have in that cable indicates something is adjusted incorrectly. Presumably the derailleur is on the smallest sprocket and is resting on the high limit rather than being controlled by the cable and shifter. That would mean your indexing adjustment is off. I'd work through a rear derailleur setup process to fix that problem first. The Park Tool Rear Derailleur article and video is has a very clear step by step process.

If that does not improve your indexing, the next thing to look at is the derailleur hanger alignment.