You can download Quicksaving on CurseForge and Modrinth:
  CurseForge:   https://curseforge.com/minecraft/mc-mods/quicksaving
  Modrinth:      https://modrinth.com/mod/quicksaving
To keep a better overview of all mods, the issue tracker is located in a separate repository.
  For issues, ideas, suggestions or anything else, please follow this link:
    -> Issue Tracker
Because of the way mod loader files are bundled into one jar, some extra information is needed to do a PR.
  A wiki page entry about it is available here:
    -> Pull Request Information
Quicksaving adds an easy way to save and load a location in-game. This can for example be used for parkour courses, where you save the initial location and re-load when you fall. The functionality is similar to those of other known games, such as Fallout and Baldur's Gate. It works in between dimensions.
It is possible to use this mod client-side only. It will use the /tp command to teleport the player to the quicksaved location. Of course you must have cheat-access enabled for this. If installed on both the client and the server, a cleaner way of teleporting is used without chat messages.
By default F6 (with crouch) is used to Quicksave, and F8 to Quickload. This can be configured to your liking.
   All available config options:
mustCrouchForQuicksave  default true
Whether the player has to crouch in order to execute a quicksave.
mustCrouchForQuickload  default false
Whether the player has to crouch in order to execute a quickload.
musthaveCheatAccessForQuickloadOnServer  default true
Whether a player requires cheat access if they want to quick load when the mod is installed on both the client and the server. NOTE: if the mod is only installed on the client, cheat access is always needed.
Hotkeys can be configured:
Here you can see the player quicksaving, and quickloading twice:
Show Spoiler
Works interdimensionally as well:
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You may freely use this mod in any modpack, as long as the download remains hosted within the CurseForge or Modrinth ecosystem.
Serilum.com contains an overview and more information on all mods available.
Comments are disabled as I'm unable to keep track of them across so many separate mod pages.
For issues, ideas, suggestions or anything else there is the Github repo. Thanks!