10x Time Speed Button (choose version with LeftAlt or MiddleMouseButton ) + Toggle Walk (instead of hold ) + Decals stay infinite.
If you don't want everything you can install one of such versions:
-decals stay + toggle walk (without time button )
-only toggle walk (without time button )
-only decals stay (without time button )
Additionally you can bind button T and B to any function you want (at default this functionality is blocked in game) - all mod versions have this.

CHANGES WHAT THAT MOD MAKES:
-Walking button now works as toggle (the same like is default in LE1 ) so just click it instead of holding it.
-Decals staying for increased time (changed to >2 hours instead of default 15seconds ). For example it works for bullet holes and cracks in glass. Decals disappear after loading save. 
-Added speed up time button (you can choose LeftAlt or MiddleMouseButton ): holding it speeds up the game x10 (works for some unskippable cinematics or when you must watch them again after death/reload and also it can be used to move faster at boring moments ). 
-in options/key bindings, you can bind keys T and B to any function you want, at default this keys are blocked and cannot be mapped to any function. In original ME3, "T" was hard bind as "chat button", in Legendary Edition they additionally blocked "B" - it was "Push to talk". Now for example you can bind "T" to Walking function (in Mass Effect 1 "T" was default button for walking ). 

ADDITIONAL INFO:
I want say one more thing, this mod is not for changing mechanics of game but making it more convenience (time 10x to not be forced to watch the same cutscene over again after death&reload, toggle walk like in LE1 ) and immersive (decals stay ).

INSTALLATION (ME3Tweaks Mod Manager needed )
1. Download preferred mod version (install only one file ).
2. Open ME3Tweaks Mod Manager
3. Drag downloaded file into Mod Manager 
4. Apply or import the mod. If you import - click mod name on the list and then click Apply Mod at the bottom right of the window.

This mod is only for Mass Effect 3 Legendary Edition (LE3 ). 

If you want you can check my similar mods for LE1 & LE2

Mod working with actual saves so starting new game is not needed.

UNINSTALL:
In ME3Tweaks click Manage Target (first make sure that location for Mass Effect 3 Legendary Edition is selected ) and find this mod: "10xTimeSpeed button. Toggle Walk. Decals" (it is in default opened bookmark: "Installed DLC Mods" ) - you can disable and delete mod.

OTHER MY MODS:
My most popular Mass Effect Legendary Edition mods:
LE2 New Game Plus Upgraded
LE2 Changes for Import Credits from LE1 save (many options )
LE3 Auto cover off
LE2 Auto cover off
LE2 Changes for Resources import bonus (many options )
LE1 QoL. infinite run and Mako boost. decals and corpses stay and physics. separate use and sprint. 10x time speed button. inventory tweaks. bullet time
LE2 QoL. mouse acceleration off. infinite run. corpses physics. time speed button. toggle walk. decals stay.

All my mods for Legendary Edition are HERE
Mods for Mass Effect Original Trilogy are here: ME1, ME2, ME3


ACKNOWLEDGEMENTS / CREDITS
Kudos for all folks who first found and share what commands and values in Coalesced files do specific things.

Big kudos for Mgamerz and ME3Tweaks Group for tools what make making and installing mods convenient:

ME3Tweaks : ME3Tweaks Mod Manager
https://www.nexusmods.com/masseffectlegendaryedition/mods/2


FAQ:
-Why LeftAlt/MiddleMouseButton for 10xTimeSpeedButton not work?
-You must have it already set as some other action in Main Menu->Extras->Options->Key Bindings. Just change those to another key. Then LeftAlt/MiddleMouseButton will be working as intended.