So I'm trying to make a homebrew feat that functions as the level 1 Oath of Ancients feature, Healing Radiance. It's a channel divinity feature that heals yourself and nearby allies an amount equal to level + pb + cha mod. How do I shorten this to just be one number in the character sheet? Specifically in the snippet section, I've written it as this: (classlevel)+(proficiency)+(modifier:cha)#unsigned. I looked at other features in the character sheet to find what language I should try to use, but it still doesn't work, it just shows what I wrote here exactly. How do I make it just be one number on the character sheet (5, for example)? 

You can check here https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/25930-using-snippet-codes-in-your-homebrew . This will help you when writing snippets for your homebrew..

Something like this, might work, but I did not test it as I don't homebrew, sorry..

{{classlevel+proficiency+modifier:cha#unsigned}}

{{(classlevel+proficiency+modifier:cha)#unsigned}} or {{(classlevel+spellattack:cha)#unsigned should also work, but I would personally use the first one just in case they eventually fix snippets to reflect stuff like magic item bonuses to spell attacks.