That's pretty much what i do, but i stick to freebased extracts, you only need HCL extract or Harmalas in salt form if you wanna separate it from other alkaloids in the full spectrum extract (which there's nothing really wrong with those other alkaloids ime).
I just boil up 100 grams of whole Rue seed, do about 4 to 6 separate boils straining/filtering each boil off into a big pot, reduce the boils and boil it all down to about 375 to 400mls, add in 75mls of vinegar, dissolve like 15 to 20 grams of washing soda into 100mls of hot water, pour/stir the washing soda water into the brew which precipitates out the crude full spectrum extract.
Once the extract falls to the bottom over say 30 minutes or so, i pour off the top water through a coffee filter (just in case) and continue pouring the extract into the filter, i rinse the measuring cup with fresh water to make sure i get all the extract out and into the filter, once all the liquid is drained through and the extract is in the filter, i dunk the open filter into about 300 to 400mls of fresh warm water with 75mls of vinegar added and make sure all the extract falls off the filter into the water and stir until it's dissolved (i also wet the filter a little bit with some extra fresh water and wring it out in the measuring cup a few times to make sure i get everything), once it's all dissolved it's filtered, re-based and filtered again, i re-dissolve, filter, re-base, and filter a couple more times or so until i have a pure full spectrum freebased Rue extract.
Once it's clean i twist up the coffee filter with the extract in it, getting out any air or moisture, put it into a paper towel and press on it to compact it but also to squeeze out any excess moisture, and then i open back up the coffee filter and let it sit out to dry, and while drying i break up the extract clumps in order to let it more fully dry. Once dry i put it into a container and can either smoke some or encapsulate some and take it orally, or dissolve it in something acidic if i want to drink it.
But with that said, i don't think simply drying an acidic extract liquid would give you a good powder, probably more of a residue, but for an actual Harmala powder, you need to do a manske extract on it which just requires 100 grams or so of salt if i remember correctly. Some people do their manskes multiple times but i've only ever done it one time and i've done the manske extraction a few times, seemed pure enough to me and was certainly different compared to the full spectrum freebased extract so i'm pretty sure one salting was enough to leave behind most of the other alkaloids.