Window Box is a Botania addon mainly adding new magical flowers and other content, with the following intentions:

Integrating Botania with newer Minecraft updates (e.g. Oxidaisel, Candysnuft)
Adding functionality that I found myself wanting while playing (e.g. Snapdresson, Manastar HUD)
Providing options for custom scenarios like skyblock or modpacks (e.g. Groundberry, portal trees)
Adding things which add to the feeling of the magical/botanical theme, or just for fun (e.g. Topsy Tulip, Bouquet)

Changes to existing content:

Manastar: Now displays a wand HUD for its targeted pool, like the Mana Pool HUD, except displaying the overall fullness of all spark-connected pools

Functional Flowers:

Snapdresson: Remembers a trinket loadout. When clicked, re-equips you with those trinkets, if you have them in your inventory.
Including within a Trinket Case or Shulker Box, etc.
Groundberry: Turns nearby Sand into Suspicious Sand, and Gravel into Suspicious Gravel, with the associated loot.
Intended primarily for skyblock.
Oxidaisel: Rapidly oxidizes nearby copper blocks.
Glory Incarnata: Prevents* and reverses the zombification of Piglins, Hoglins, and Villagers.
*except for preventing villager zombification, as this happens via death.
Witch's Pupil: Allows remote observation of the flower when one of its Eye Berries is plucked and eaten.
Dispelagonium: When splashed with a potion effect, clears that effect from nearby entities for the duration of the potion.
Also added are potions for Wither, Mining Fatigue, and Levitation.
Topsy Tulip: Can be placed on any side of a block, and warps gravity to let you walk on walls.
Requires Forge GravityAPI.

Generating Flowers:

Candysnuft: Generates mana when nearby candles are extinguished (consuming a candle), but only in small portion sizes (blocks of at most 3 candles).
Queen Anelace: Sits on a square of Grass Blocks and outputs redstone signals pointing to a block in that square; generates mana if that block (and only that block) is broken.

Magical Trees:

Chthonic Yew: A tree with dark black wood whose hollow contains a Nether Portal; a growable alternative to manual placement.
Alfthorne: A great tree with vibrant green wood whose hollow contains an Alfheim Portal. Requires the same mana infusion to open.
Intended as options for modpack progression.

Miscellaneous:

Bouquet: A decorative item which can bundle up to 3 flowers together.
Rod of the Acropolis: A survival-friendly version of the Debug Stick which can force the shape of Stairs, Fences, Walls, and Panes.
Rod of the Grasslands: A simple upgrade to the Rod of the Lands which creates Grass Blocks instead of Dirt.

Botania: Window Box