I've been needing to create a feat with a proficiency prerequisite, but the only 3 in there right now are for light armor, medium armor, and heavy armor.

Is there any plan to add tools, weapon types, etc. to this list?

Specifically, one of my characters took the Burglar feat (Unearthed Arcana, 6 June 2016).

You pride yourself on your quickness and your close study of certain clandestine activities. You gain the following benefits:

• Increase your Dexterity score by 1, to a maximum of 20.
• You gain proficiency with Thieves' Tools. If you are already proficient with them, you add double your proficiency bonus to checks you make with them.

Unfortunately, I cannot create a feat that is as complex as:

if (ThievesTools = Proficient) {
    Double ThievesTools Proficiency
} else { 
    ThievesTools Proficient
}

So I am force to create 2 separate feats. One with regular proficiency, and one with double proficiency. But even then I'd like to put a prerequisite on the double proficiency feat that you must already be proficient in Thieve's Tools. But I can't even do that. If I'm having this sort of trouble with my own private homebrew feats, I just don't know what sort of trouble everyone else is having.

Yeah. having the same problem. Can only select from Heavy Armor, medium Armor, Light Armor. No way to pick a weapon proficiency, tool proficiency, or any other proficiency. 

Seems pretty clearly a mistake. Please fix.