This is the save anywhere mod. This mod allows users to bind a key on their keyboard to allow them to save the game *anywhere* in Stardew Valley.
The two known exceptions to this mod where it is known where the player can't save is in the Community Center and in the Sewers.
When the game is saved and reloaded from the save the player will be warped back to their previous location, and the game will simulate game time at a faster speed to help reposition all of the NPCs. This is intended to allow the player a bit of reprieve before going back into the swing of things but can be disabled via the config file.
If you have any issues or questions leave me a comment. Thanks!