Is it possible to add more saved toolbars without mods in Minecraft?
Solution 1:
No, this can not be done. But you can prepare multiple files in your Minecraft folder and rename the one of them to hotbar.nbt that you want to use next. Then you need to restart the game to apply it. Until then, you can keep using the old hotbar file.
Note: I tested this on Linux. File handling might be done differently by Minecraft on Windows.