You can download Stack Refill on CurseForge and Modrinth:
  CurseForge:   https://curseforge.com/minecraft/mc-mods/stack-refill
  Modrinth:      https://modrinth.com/mod/stack-refill
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
Stack Refill is a utility mod which automatically refills the itemstack in the player's hand if there is any of the same item in the inventory. It works for weapons in combat, tools used on blocks, stacks when placing blocks, eating food, using potions, tossing items on the ground, drinking milk buckets, when breaking a fishing rod and should work with all modded blocks. One of my personal favourite quality of life tweaks.
Has to be installed on both the client and the server for the best reliance. Can be used server-side only, but this may cause some visual desyncs.
A sword being replaced during combat:
Show Spoiler
A shovel being replaced when digging dirt:
Show Spoiler
Log blocks being replaced while placing them down:
Show Spoiler
Bread being replaced after consumption:
Show Spoiler
Potions being replaced after consumption:
Show Spoiler
Items replaced after being tossed:
Show Spoiler
A milk bucket being replaced after being consumed:
Show Spoiler
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A fresh fishing rod after its last use:
Show Spoiler
When using items on (modded) blocks, such as a sieve from Ex Nihilo:
Show Spoiler
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!