Yes, but it’s a little wonky
Harvestella is finally out on PC and Switch, and as usual, the PC edition is having some growing pains. While mouse and keyboard support is technically in with Harvestella, it’s a bit annoying when it comes to functionality.
Harvestella mouse support for menus is shoddy at launch
There is mouse support on Steam/PC, but it doesn’t fully work in tandem with the game’s menus. The issue arises when trying to select menu options, as you can only click to confirm in menus: but you can’t select menu items. Instead, you’ll need to move around menu options with your keyboard (using the arrow keys), then select an option through left-clicking. This includes clicking through dialogue, the pause menu, and pausing cutscenes.
Harvestella does have mouse support in-game, at least
Note that when you’re actually playing the game, the mouse does work while you’re utilizing a keyboard (and WASD movement) to shift the camera around. At the very least, your mouse will be supported in some fashion if you choose to play without a controller (which is also supported).
Full-menu-mouse-support is likely something that’s going to be added in a post-launch patch (though not confirmed), as it’s not typical for PC games to launch in 2022 like this; and stay that way after fan complaints. For now, just be aware of it if you get the game on PC.