There are a couple of potential issues at play here. One is when startches from the rice intermix with the boiling water and steam, which creates a residue. This could be the "slime" you are referring to.

Another is when meat is cooked, some of the proteins coagulate and form a "scum" that, when making soups or broths, gets skimmed to keep the appearance more clear.

I wouldn't worry too much about either one, other than in terms of messiness. If I'm going to mix chicken in and use my rice cooker to make a combined meal, I'd use cooked chicken (chop it up, cook it in a skillet ahead of time, or use leftovers from a bigger chicken meal). This would reduce the "protein scum" issue from the chicken, I think, vs using raw chicken.

There are a couple of potential issues at play here. One is when startches from the rice intermix with the boiling water and steam, which creates a residue. This could be the "slime" you are referring to.

Another is when meat is cooked, some of the proteins coagulate and form a "scum" that, when making soups or broths, gets skimmed to keep the appearance more clear.

I wouldn't worry too much about either one, other than in terms of messiness. If I'm going to mix chicken in and use my rice cooker to make a combined meal, I'd use cooked chicken (chop it up, cook it in a skillet ahead of time, or use leftovers from a bigger chicken meal). This would reduce the "protein scum" issue from the chicken, I think, vs using raw chicken. The taste is a better than boiling raw chicken, to me, but that's just my opinion.