Experiment around, but be careful/cautious. Try out some different plants with the Rue and see if anything good comes from it. Lemon EO for example, can clean up Rue's body load quite well, as well as taking away the nausea/vomiting, and with Cannabis in the mix, things can actually get a bit Psychedelic ime. There's also Lemon Balm, which cleans up the body load, but ime doesn't reduce nausea/vomiting. You could also perhaps try finding a plant or essential oil or something, that can inhibit CYP2D6, which if i'm not mistaken CYP2D6 is one of the main enzymes that metabolizes out the Harmalas, which the Harmalas themselves are not only CYP2D6 substrates, but are also inhibitors of CYP2D6, which could inhibit the Harmala's metabolism, and might contribute to the reverse tolerance build up, but idk.
But, if you're wanting to potentiate the Rue, try taking it daily or every 2 to 3 days for a couple or so weeks, it builds up a reverse tolerance, which makes the Rue stronger each time you take a dose, and as the reverse tolerance builds up, the nausea/vomiting, as well as body load gets reduced significantly, ime. And Lemon EO can be used to help clean up the Rue while building up the reverse tolerance, so that you don't get nauseous or vomit at all, which imo is pretty cool.
Also with the Lemon EO, the Limonene seems to stay in the system for i'm thinking a couple of days, due to it's long half-life. So while i was taking it every day, it kept building up and started dulling down some of the Harmala effects, but when i start taking the Lemon EO again, i'll probably skip a day in between and take it every two days and see how that goes, maybe three days. I usually use between 4 to 6 drops of Lemon EO (in a capsule, undiluted), but 5 drops seems pretty good for me. With Lemon Balm i take 2 to 4 grams, usually 3 grams but sometimes i'll go with 2 grams.