How hard it would be to add another health bar for 5e?

[MestreDosGados]

I was wondering about trying to implement a new homebrew rule to my tables, but i would need another health bar.
How hard it would be to add another health bar to 5e ruleset? It would just need to appear in the combat tracker, but it would be nice if it appears at the character sheet too.
I would like if it also applies to monsters when they are sent to the combat tracker. I would not mind if a need to manipulate the values of this health bar manually.

[Laerun]

Depending on how it works, you would probably need to write or alter an extension.

[MestreDosGados]

Yeah, i'm expecting it would need to be done by an extension for sure, but how hard it would be to develop a extension like this?

[Trenloe]

but how hard it would be to develop a extension like this?
If you're familiar with Fantasy Grounds coding it will be relatively straightforward to implement a linked field in the combat tracker. If you're not familiar with FG development then you'll need to familiarize yourself with the FG GUI, FG control placement with XML and FG LUA scripting (to a lesser extent), the CoreRPG/5E combat tracker layout (any maybe the character sheet layout as well), and how to layer your extension on top of the base FG code. So, depending on your experience and knowledge, it could be straight-forward or quite hard...

[LordEntrails]

Look at one of the Sanity and Honor extensions, they do something very similar.
https://www.fantasygrounds.com/forums/showthread.php?45467-5E-Add-on-Sanity-amp-Honor

[Trenloe]

Look at one of the Sanity and Honor extensions, they do something very similar.
https://www.fantasygrounds.com/forums/showthread.php?45467-5E-Add-on-Sanity-amp-Honor
I think that originally did have fields in the combat tracker, but they were removed - and now there are fields in only the character sheet and the NPC sheet. So it's an example of adding fields in the sheets, but not the combat tracker.