Can you import bank data where mortgage and investment accounts linked together?

Thanks for posting in the Community, @beth36. 

Currently, the option to link the mortgage and investment accounts together when importing bank data from Quicken to QuickBooks Online (QBO) is unavailable. As an alternative, you'll first have to set up a liability account so you can record the loan/mortgage and its payments. I'd suggest consulting your accountant to determine the appropriate account to use before performing the steps below on how to set up a liability account. 

1. Go to Accounting from the left menu. 
2. Select Chart of Accounts.
3. Click New.
4. Choose the appropriate account and detail types. 
5. Enter a relevant name for the account. 
6. In the Unpaid balance field, enter the full loan amount as negative. Then, choose the initial date. 
7. Click Save and close.

The screenshot below shows you the last four steps. 

Once done, record the money you got from the loan and its payment. For more information, see the second and third steps through this article: Set Up A Loan. 

For your investment, you'll first have to set up an equity account. After you receive the investment and you'll need to pay it back, record it either an actual check, debit, or a credit card. For detailed steps, check out this article: Track Personal Money or Investments To Your Business. 

After that, let's enable the multicurrency feature in the settings. Please take note that you're unable to turn it off once it's turned on. Here's how: 

1. Go to the Settings (Gear) icon at the upper right. 
2. Select Account and Settings under Your Company. 
3. Go to Advanced from the left menu. 
4. Choose Currency.
5. Select your Home Currency.
6. Check the Multicurrency box and confirm the change. 
7. Click Save.
8. Choose Done. 

I'd suggest visiting this website: Multicurrency Overview. This link provides you steps on how to add currencies, delete them if there are no transactions attached to them, and create an account that uses foreign currency. Afterwards, you can assign multicurrencies to your customers. 

I'm always here to help if you need anything else. Have a good day, @beth36.