I want to add UI elements, but unsure where to start.

[ResplendentDarkness]

I'm feeling fairly confident with adding new races and classes now after seeing where I made some mistakes with manual XML editing but want to start learning how to add to the UI. Like I did not see anyone that has incorporated the Drop Dead Studios, Sphere system. I'm not sure what I need to be looking into to add like a new tab to the character sheets for the altered magic effects or if I want to go in and add for caster level and spell point elements to combat tab, etc. Any pointers for where to start researching?

[damned]

Find a basic extension - eg one that only changes one or two things and then pull it apart and see how things work.
You might try something like one of the Sanity extensions for 5E or Hero Points extension.
Adding an extra tab - start with record_char.xml and you will see the references (at least 2) required to add another tab - usually record_char_something.xml

Start small - work out how to add one thing at a time only.

[ResplendentDarkness]

thank you, so I have the Hero Point extension and I can see some of how it alters some elements but where do I find the base character sheet file to compare what they're altering vs the original state?

[LordEntrails]

thank you, so I have the Hero Point extension and I can see some of how it alters some elements but where do I find the base character sheet file to compare what they're altering vs the original state?
Things are going to be inherited. So they Start with the CoreRPG Ruleset, then the 5E Ruleset, then the Extension. Typically files will have same/similar names. The recommendation usually is to make a copy of the rulesets, extract them, then use Find in Files from Notepad ++ for the string you are looking for.

[damned]

Same as with extensions. The .pak file is a renamed .zip file...

[Bidmaron]

Recommend putting the unzipped somewhere other than rulesets directory or you will forget at next upgrade and wonder why things aren’t working because an unpacked ruleset takes precedence over the .pak file. I have an unpacked rulesets folder I keep all my unpacks in

[Trenloe]

See this thread: https://www.fantasygrounds.com/forums/showthread.php?19033-Modifying-the-3-5e-PFRPG-ruleset

[ResplendentDarkness]

thank you, that all helps a lot.