My CA retirement doesn't withhold state taxes outside of CA, but I have extra withheld to pay KS income tax I owe every year. Is that deductible?

If you are a resident of Kansas you should not have any California state taxes withheld on your pension income reported on a Form 1099-R in box 14.  If you have Kansas state taxes withheld and reported in box 14 of the Form 1099-R those taxes are deductible on Schedule A as an itemized deduction.  This is done automatically by the TurboTax program.

To enter state income taxes paid -

Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credits
Click on I'll choose what I work on (if shown)
Scroll down to Estimates and Other Taxes Paid
On Other Income Taxes, click on the start or update button

On the next screen scroll down to Other Income Taxes Paid in 2023

Or enter state taxes paid in the Search box located in the upper right of the program screen. Click on Jump to state taxes paid

How do you have it withheld if they don't take out KS withholding?  Or do you mean you have more federal tax withheld?  Yes you need to enter it on your tax return  unless it's part of your 1099R retirement in box 4. 

If you pay state withholding or a state tax due you can enter it on your federal tax return as a deduction.  But it is only used as a deduction if your total Itemized Deductions are more than the Standard Deduction.  There is a max 10,000 limit (5,000 MFS) of property tax and state taxes "SALT". SALT is State And Local Tax. Which includes property tax, any state tax paid like for last year’s return and includes any state withholding from your W2s and any 1099s you have. And any taxes in W2 box 14 and 19 like SDI or VDI. You can only deduct up to 10,000 (5,000 MFS) for SALT State and Local Taxes.

For 2023 the standard deduction amounts are:

Single 13,850 + 1,850 for 65 and over or blind (15,700)

HOH 20,800 + 1,850 for 65 and over or blind (22,650)

Joint 27,700 + 1,500 for each 65 and over or blind (29,200/30,700)

Married filing Separate 13,850 + 1,500 for 65 and over or blind (15,350)