This does have the ability to save and load skilltrees with more than 15 points, but keep in mind that if you try loading a skilltree with more than 15 points on a vanilla server that doesn't support it, the game will just reset your skills when you spawn in.

Will this have the ability to save Preset Skill Trees that have more than 15 points?

@Dopper Yes, but I can reset my points in the menu and decide what to put during the game, right?

If I have all 15 points available.

Good suggestion! I've pushed an update to let you save presets in-game with the skill tree menu, it won't allow you to load presets in-game though since that'd cause problems.

Can I add presets in-game?

While playing, I can do this in the in-game skill tree menu.