Good morning, @WWWatPremierCreativeGroup.
It's great to see a new face here in the Community. I can provide you with some information about custom fields and give you answers to your questions.
For the first question you asked, there isn't a way to add custom fields to journal entries. However, I'll give you two articles to give you more details about both of them and what they can do:
As for your second question, it seems like you want to apply multiple job numbers to a single bill. This won't work because QuickBooks Online allows for one of each custom field per transaction. Perhaps you could separate the job numbers by a comma within one field. If that doesn't work, I would consider using a different feature like tags.
I hope this helps answer both of your questions. If you need any more assistance, don't hesitate to ask. Best wishes!
