Possibly. There are no perfect treatments. Anti-viral and anti-fungals have been helpful in some patients. Herbal supplements like clove, thyme, and oregano which have anti-viral and anti-fungal activities could help if ingested. Topical vit d oil might be beneficial. Check blood 25-oh vit d 3 and see if it is low. Topical or oral coconut oil which is both anti-viral and anti-bacterial might be helpful.
Nothing is approved. Nothing has been approved in the US as far as herbal supplements to treated leishmaniasis. I bet you may find tons of anectodal success stories, but I would strongly suggest not to experiment to let the disease progress and get it advanced that it would be really difficult to treat.