I've found that tweaking the _metadata file to include the code
"requires" : ["QuickbarMini"]
fixes the issue that I and Kimmu were having where the healthbar either never shows up in the quickbar (or only sometimes shows up) by forcing Quickbar Mini to load first. That is, as long as both mods are loaded from the same source (i.e., both from steamapps\workshop\content\211820 or both from Starbound\mods).
https://i.imgur.com/pzrpnDF.png