Yeah, very cool - I was not aware of that Utilities functionality in Zapier!
Thanks, I really appreciate the answer, Ill get to work on that until I get stuck again 
Glad to help where I can.
You can get the ids of your custom field options using the Asana API Explorer.
First step is to get the id of your workspace/organization. Do that by using these settings:
That will get you a list of all of your workspaces (or workspace if you only have one). Grab the “gid” of the one you want.
Then use these settings:
Down below, paste in the gid of the workspace you copied.
That will get you a list of all of the custom fields in the workspace, and for each field that’s a dropdown list (an “enum” field in technical terms), it will list you each option and its gid. Its those option gid’s that you need for Zapier.
There’s no easier way that I know of than using Zapier’s lookup feature.
FYI also my tool Custom Field Explorer can give you the GID (that’s a paid feature though)
I actually checked that before I posted here - it shows the gids of the custom fields but not of the enum options, right? So doesn’t help in this case.
Indeed you are right but I realized it the other day and could fix it within minutes if needed. (actually I’ll try today)
I just deployed it! List all custom fields of an organization - #28 by Bastien_Siebman
This still works! Lookup tables are now in the Formatter by Zapier → Utilities → Lookup Table
Thank you, again!