You'll probably have to draw this out so I'll explain it to the best of my
ability:



I have an outside light and an inside light connected to a set of 3-way
switches. When switched, both the indoor and outdoor lights go on/off
together.



The 3 way switch in the basement has 1 cable with black, white, and red
connected to the switch. The 3 way switch upstairs (the one in question)
has 4 cables coming into the box and is connected as follows.



Cable 1 (assumed power feed)

- Black connected to different colored terminal on switch

- White twisted together with 2 whites (from cable 2 and cable 3).



Cable 2 (assumed cable from indoor and outdoor lights)

- Black twisted together with black from cable 3 and white from
cable 4.

- White twisted together with 2 whites (from cable 1 and cable 3).



Cable 3 (assumed kitchen light)

- Black twisted together with black from cable 2 and white from
cable 4.

- White twisted together with 2 whites (from cable 1 and cable 2)



Cable 4 (from downstairs 3-way switch)

- Black to terminal on 3-way switch

- Red to terminal on 3-way switch

- White twisted together with 2 blacks (from cable 1 and 2)



My goal is to use a combination 1 single pole and 1 3-way switch to have the
inside light be connected to the 3 way switches and the outside light to be
switched normally from the location in question. The Leviton switch I
bought (CAT 5241) works such that the top switch is a 3-way and the bottom
is a single pole standard switch.



When I wired up the new switches, I didn't realize that the kitchen light
was involved. I assumed the 4 cables were incoming power, link to 3-way
switch in basement, outside light, inside light. It appears that I was
wrong because now I have a mess (top switch controls inside and outside
lights in conjunction with 3 way switch downstairs, bottom switch controls
kitchen light based on the state of the top switch). Although the set of
3-way switches (switch in basement and top switch upstairs) is behaving
correctly, the inside and outside lights still go on/off together. My new
assumption is the outside light is wired to the inside light and comes down
from the inside light to the 3 way switch as cable 2. I'm guessing that
cable 3 is from the kitchen light.



Do my assumptions make sense? Without running more cable, is there
accomplish what I want?



Thanks everyone for reading such a long post.