Go to the ingredients page and enter a dummy pg source. Just type in pg, and enter it in as 100% pg.
Now, when you go to the recipe page, add that dummy pg source into the recipe and enter all the other information. It will have you adding a certain amount of pg, but now you have to adjust the VG/pg ratio, because you don't have pg to add. Your final VG pg ratio depends on how much nicotine and flavorings you add and you will not be able to adjust it, except by altering the nic concentration or the flavor concenteation.
You can just guess and plug numbers in for your VG% and run the calculator until you hit on the VG % that has you adding 0 ml of straight PG. Or, you can calculate it out. Like this:
Your nic and flavors are in pg, so you have to add up the percentages of those. Example:
Say, you are making
30 ml
5% each of flavors A, B, and C (all in 100% pg or close)
6 mg/ml (using your 36 mg/ml in pg as the source)
Your flavor percentage adds up to 15% (5% * 3 flavors = 15% total).
What % of the mix does the nic in pg make up?
You would add 5 ml of 36 mg/ml nic in pg to 30 ml (the calculator tells you this), so 5/30* 100 = 16.7%
So the total pg you are adding to the mix is 15% (from the flavors) + 16.7% (from the nic in pg) = 31.7%
31.7% of your mix has to be pg. The rest can be VG. Change the VG to 68.3% (100-31.7).
Now your recipe should give you back 0 ml as how much pg to add.