The new DLC for is pretty straightforward, but there's a point that might trip you up if you haven't been making potions or using herbs. Finding some Valerian [[link]] for Kvyetoslava is a step in the Source of Inspiration quest, as you help the grandma recall the location of the shrine of Veles—a pagan monument that the painter is very interested in visiting.
Here I'll explain the quickest way to acquire some Valerian in this quest, but also more generally, some other ways you can get it, in case you just need some to make a specific potion.
Where to find Valerian in Kingdom Come: Deliverance 2
You can find Valerian (a small white flower) by "Forest paths, mires and peat bogs, everywhere that the ground is damp," but if you specifically want it for Kvyetoslava in the Brushes with Death DLC, then you can find some right next to her house in Vidlak Pond. From just outside the tanner where she sits, go a little way north to find a flowery meadow by a stream—there's a lot of Valerian here. Generally, you'll find quite a lot of Valerian near water sources.
If you're still struggling to find fresh Valerian, or you need it [[link]] for something else other than the Brushes with Death quest, you can also buy it fresh from Aranka in the Nomad Camp, or buy its dried variant at pretty much any apothecary, including the one in Troskowitz.
Since it's dried, it'll also last much longer for all your alchemical purposes. As with any herb, if you're using it to regularly make potions, I recommend stockpiling a large quantity of dried, or simply making whatever potion you need in bulk so you [[link]] don't have to worry about freshness.
Bring the five Valerian back to Kvyetoslava and you'll be one step closer to helping her remember the shrine of Veles' location, so you can bring the painter there.