Overview: This mod grants all characters the ability to short rest without healing, as a toggle-able ability. Due to current modding limitations, this requires modifying the Hide action to grant you the ability to short rest (this incompatibility is easily resolved in saves after you've hidden at least once, see instructions.)

Requirements: 
BG3 Mod Fixer

Vortex or BGMM Installation:
1. Download the file. 
2. Use Vortex or BG3 to navigate to the folder you downloaded the file in, and select the file to add to your available mods.
3. Add the mod to your list of active mods at the bottom. Don't worry about incompatibilities with other mods which alter the Hide action for now, this is temporary. 
4. Load into your save file, and have at least one of your characters perform the Hide action. 
5. That character should now have a new Toggle-able passive. Save and exit. 
6. Adjust your load order to prioritize any other mods which alter your Hide action; you should be able to spread the ability to short rest without healing to your while your new power is toggled on, added as a new common ability. 

Manual Installation: 
1. Download the file. 
2. Unzip the contents to your (. . .)AppData\Local\Larian Studios\Baldur's Gate 3\Mods folder. Filepath may vary based on OS, if you're here then you know what you're dong. 
3. Modify the modsettings.lsx file found in your (. . .)AppData\Local\Larian Studios\Baldur's Gate 3\PlayerProfiles\Public folder by adding the following lines: 
    3a. After the last entry in the <node id="ModOrder"> section but before the </children> line, add these lines:
           <node id="Module">
              <attribute id="UUID" value="a0a373ec-5f34-4bb9-93b7-640f571d51a0" type="FixedString" />
           </node>
    3b. In the <node id="Mods"> section, add these lines: 
           <node id="ModuleShortDesc">
              <attribute id="Folder" value="Unlimited No-Heal Short Rests" type="LSString" />
              <attribute id="MD5" value="" type="LSString" />
              <attribute id="Name" value="Unlimited No-Heal Short Rests" type="LSString" />
              <attribute id="UUID" value="a0a373ec-5f34-4bb9-93b7-640f571d51a0" type="FixedString" />
              <attribute id="Version64" value="36028816346316888" type="int64" />
            </node>
4. Load into your save file, and have at least one of your characters perform the Hide action. 
5. That character should now have a new Toggle-able passive. Save and exit. 
6. Adjust your load order to prioritize any other mods which alter your Hide action; you should be able to spread the ability to short rest without healing to your while your new power is toggled on, added as a new common ability. 

Usage:
In your passives menu, you should have a new, toggle-able passive ability with an icon identical to the Song of Rest action. Toggling it on will prevent you from regaining healing and grant you a spell (available in your common actions) which grants the same toggling passive to all party members nearby. To avoid unlimited healing, make sure that all of your allies have been granted the ability and all of your allies have their toggles synchronized (spreading the effect while toggled does not make the receiver automatically match your current toggle state and I don't know how to fix that.) After everyone has performed their very first no-heal short rest, their short rests should from then on be synchronized.

Compatibility:
This mod should be compatible with just about everything. Just make sure that you've performed the steps to adjust the load order before and after one of your characters gets the toggle-able passive so that any other mod which alters the Hide skill overrides this mod upon installation completion. Mods which add new action resources which replenish on a short rest should be fully compatible with this mod, as should mods which alter your normal short rest ability. This mod calls the ShortRest() functor, so anything which alters said functor will also alter the short rest effect from this mod in the same way.