When making chicken and dumplings thicker you want to add some more flour to the dumplings.
Thicker chicken and dumplings need more flour added to increase the thickness of the dumplings as well as the broth in the chicken and dumplings.
If your chicken and dumplings are too thin then you're not using enough flour.
Just dust the chicken and dumplings with some more flour until the chicken and dumplings become thick enough for you.
Add a little bit of flour at a time so that you don't add too much flour.
Just dust the chicken and dumplings with additional flour a little bit at a time and stir the chicken and dumplings until they become thick enough.
My grandma taught me this way to thicken my chicken and dumplings and the flour addition to the chicken and dumplings has always thickened them.