"I would like to record those transactions in quickbooks for tax purposes but I do not want to link them to any bank account."
And yet, they obviously are Paid, somehow, using Funds, from somewhere.
"For
example, while in training, I did not charge customers for nutrition
visits but they did pay for their whole food supplements. I deposited
income for the purchase in my personal checking."
Then I recommend setting up one Bank account and name it Owner Funds or Cash On Hand.
"Also, I purchased
wholesale supplements using my personal checking."
Checking, credit card, or cash; all you need is one Bank account to represent Owner Paid and Owner Kept revenue from sales.
"I do not want to add
my personal checking account to my quicken business."
You never link a personal bank for business purposes, and you don't need to Link an account at all, even if it is a real bank account.
"However, I do need
to record the transactions for record keeping purposes."
You did not mention the business Entity Type; if this is a corporation, then instead of Bank Type, use Credit Card Type, as "liability" and name it Owed to Shareholder. Now use the data input tools for "credit card Charges" to show you made these purchases on behalf of the business, and this creates the running balance to repay you.
In either case, you need to process Sales, and then "deposit" either to Owner Bank, or against Credit Card account Balance.
"I need to record income to me and vendor purchases to others...without linking a bank account."
You don't need to link anything, ever. That is Optional.