According to Mailing your return on page 10 of the Instructions for Kansas 2019 Individual Income Tax,
- Enclose Schedule S if you have a modification on line 2, if you filed as a nonresident or part-year resident, or if you itemized your deductions for Kansas
- Enclose Form K-40V if you are making a tax payment
- If your K-40 is filed with a Kansas address, do not include a copy of your federal return; however, keep a copy of it in case the Kansas Department of Revenue requests it at a later date. If your K-40 shows an address other than Kansas, you must enclose a copy of your federal return (1040, applicable Schedules A-F and Schedules 1-3)
The Department of Revenue does not require that you enclose copies of W-2s or 1099s with Form K-40.
Additional requirements can be found by searching "enclose" in the pdf linked above.