This is a tool for quickly checking various addons so you can see if they will work together without checking all of the packs in game. It does not guarentee compatiblity, howeverr it does check the very basic items.
As a feature the tool has 2 basic packs that can added in to any behavoir pack. This allows you to have one player sleep or death counter.
To check 2 packs first browse for core pack that you want to focus on. Next press the "cross check a pack". A browse window will pop up. Select a second pack It will check if the pack duplicates entities modification. If the packs do it will give you a warning about what entities may be broken. If not it says the packs are likely compaible.
To add 1 player sleep or a death counter to a pack, first browse for a pack to be the "core pack". select the check boxes for the version of things you wish to merge in. and click merge packs. This should produce a new pack next to the program that adds in the new functionality.
Note, what pack is the core pack may impact compatiblity with other packs, so check compatiblity after doing the merge, if the pack becomes in compatible after the merge, (but was before the merge) merge 1 player sleep and death counter into the other pack that contains minecraft:player changes.