Are there situations when you a 1K dialysis bath as a long-term outpatient prescription for patients with ESKD?

I cannot think of a situation where this would be needed, and based on available data I recommend against it.

In the hospital setting, there is some data that doing dialysis with a 1K bath is beneficial and can reduce mortality, see Singh et al., PMID 34476092.

The same cannot be said for long-term dialysis patients. In fact, lower dialysate potassium concentrations were associated with increased mortality in both the DOPPS data and other observational studies, for example, Ferrey et al., PMID 298...

I do. Patients who consistently have serum potassium of close to 6 or higher pre-dialysis. I use a combination of this technique and potassium binders. As an estimate about 10-15% percent of my dialysis patients are regularly on 1k bath.