Hey, I was hoping somebody could help me create this spell that I've had in my head for a while. I'm still very rusty with the homebrew spell tools and would appreciate it if I could get any assistance with making it work well and proper.

It might be easier than you think. Tell us about your idea and we'll see if we can help.

The idea I had was for a spell that shoots two cones that are the same size and damage of burning hands, except one is fire and the other is ice. If the cones are aimed in the same 15 ft cone then it grows to 30 feet and the targets make a single save against both damages. And I have next to no idea if something like that is even possible.

You would mostly just copy burning hands and just add the details about the ice cone.

But what about scaling for the two separate cones, and the split range part?

I would use the 15 ft cone as the base, and then indicate that it has a special range. Then you merely say so in the description. Most of the spell is in the description for most spells, that's why I said it might be easier than you think.

"This spell creates two separate 15 foot cones originating from the caster: One cone dealing Fire Damage, the other dealing Cold Damage. Each creature in a 15-foot cone must make a Dexterity saving throw. A creature takes 3d6 of the designated damage on a failed save, or half as much damage on a successful one. The Two cones created in this manner cannot intersect.

The caster can, however, choose to combine both cones into a single 30 foot cone originating from the caster. Each creature in a 30-foot cone must make a Dexterity saving throw. A creature takes 3d6 Fire Damage and 3d6 Cold Damage on a failed save, or half as much damage on a successful one."

That seems to be the most straightforward way to describe it, although there's room to add flavor and descriptions. As well there's probably some need to rebalance it a bit and decide on what spell level it should be.

That sounds really good for the description, but for displaying it on a character sheet, how would you do the damages with proper scaling showing, or is that a thing you can even do when it does two damages?

Yes, it's quite easy. You have two modifiers. The first being Modifier Type: Damage and Modifier Subtype: Fire, then the second being Modifier Type: Damage and Modifier Subtype: Cold. Make sure you have the Dice Count and Die Type set for each of them, then your good to go.

Something like this?

Nice, that actually looks perfect, and was actually the same name I have for it in my head, too. Thank you very much for the help, and thank everyone else who posted, too.

No problem. FYI, that took about a minute. Here’s how you make it yourself: 

A) Start to make a spell using Burning Hands as the basis.

B) When it takes you to your Copy_of_Burning_Hands do five things: 1) Change Name, 2) Change Level;3) Give it a version number, 4) Change description however you like. I copy/pasted transmorpher’s; 5) Save!

C) Go into additional information and check the box to flag the are as “special.” Save!

D) Look at the “modifier” for the fire damage and “Add modifier” to replicate it for the cold damage. 

E) Look at the “scaling” for the fire damage and “add scaling” to replicate it for the cold.

And you’re done.  Now you know how to do it yourself in future.