So your level 3 Cornac character has a category she wants to unlock with her extra category point, but it only becomes available at level 10. Or your Wyrmic character is hoarding points to spend in Wild-Gift/Harmony when he gets it unlocked. That leaves you with a semi-permanent yellow double-up-arrow level-up marker, though, making it inconvenient to distinguish between points you want to save and points you want to spend.
My experiments in fixing that have led to the
"Save" Talent/Stat Points addon. The idea is that you can now right-click on the level-up marker to mark your current unspent points as "saved". If you have saved points but no unsaved points, you'll get a distinct level-up marker:

(The Minimalist UI isn't a particularly easy UISet to override bits of, so what I can do here is kind of limited...) As you can see here, saved points are tracked separately for each party member.
This is a work in progress, of course, so I welcome suggestions for improvement.
[edit 2013-11-12 11:58pm:
Technical info:]
Code:
Superload:
mod.class.uiset.Minimalist:
displayPlayer() [to apply our "saved" points indicator]
displayParty() [to add "saved" points indicators to party icons]
mod.dialogs.LevelupDialog:
createDisplay() [to hijack the top buttons as 'save-points' buttons]
onUseTalent() [to update the button labels]