granting proficiency bonus from racial hit dice
 

I am trying to implement a new race in the editor, and it seems that racial hit dice are not granting any proficiency bonus. Is there any explanation for this? How could I fix it?

I'm not sure what you're trying to do here. I don't know of anything in 5e where proficiency bonuses are granted based on hit dice.

Proficiency bonus increases based on a player's total class levels, increasing by one at total levels 5, 9, 13, and 17. For monster races (you pick on the Hero Lab editor whether a race is a player race or NPC/monster), it increases based on the CR, which you also have to specify on the editor. I don't know off the top of my head what CR levels those increases occur at, but they do work properly in HL.

Ok, thanks for the info. If I understand correctly, this means that a monster with class levels will generally have a lower proficiency than if all it's cr were from racial sources/all from class sources, right?

To be honest, I have no idea how class levels vs monster race levels/CR interact when it comes to HL's calculation of proficiency bonus. I usually don't assign class levels to my NPCs, instead using the columns about spellcasting then assigning the "class" from the appropriate drop down.

Alternatively, I'll program in some special enemies as player characters, with the PC calculations instead.

Monster CR proficiency is about the same with increases at CR 5, 9, 13, 17, 21, etc...

If you try to follow the DMG math,

CR 1 creature is a good even match for 4 1st level PCs - or 1/4 a CR per level.
CR 2 creature, 4 2nd level - or 1/4 a CR per level
....
CR 10 creature, 4 10th level - or 1/4 a CR per level
...
etc.

In my experience, HL seems to add the class levels - 1 to the CR.

For example, you take an Ogre and give it 4 class levels and HL says that it is CR 5 (base 2 + (4 - 1)), which increases the proficiency bonus to +3. A 4th level PC would only have a proficiency bonus of +2. So it actually increases faster than I would expect.

Using the DMG logic, an Ogre with 4 class levels should only gain 1 CR and no proficiency bonus.

ALSO, and this is the big one. According to the DMG (I don't remember the page), when you add class levels to a monster you are supposed to get the same HD for the class level as the base monster, so regardless of class if you have Large creature, each class level is supposed to grant additional HD of 1d10, not the 1d6 of a wizard or the 1d12 of a barbarian, etc.

HL doesn't do any of that correctly.

So best to custom make a creature each time and calculate CR manually.

Thanks for the info! I'll be honest, it sounds a lot like "The system is a hot mess and the 'right' solution isn't necessarily good, so do whatever"