Hi all. Is there any way to add the situational advantage symbol to both custom skills (such as those shown on Rune Knight fighters with active runes)? 

For example, I'm playing a Ranger with the old-style "Favoured Enemy" and "Natural Explorer" features. I have manually added skills to my sheet to demonstrate expertise in skills relating to my Natural explorer feature (e.g. "Coastal Survival"). Is there a way for me to also add the advantage symbol, so I can remind myself that I would have advantage on tracking favored enemies (should they be in Coastal terrain)?

I have found a workaround for "standard" skills (i.e. Survival) by making the subclass homebrew, and then adding a feature that displays advantage using modifiers - but it would be great if there was a checkbox or something on skills so that this information could be added directly via the character sheet.

Any help, advice or wisdom appreciated. Thanks!

The character sheet can't handle temporary effects, which is essentially what this is. For my ranger I made an item that granted the bonuses, and equipped and unequipped it when I was in the relevant terrain.