This could be useful for various different reasons. Most commonly we have been asked this for leases that have multiple tenants, and the Primary tenant moves out, but the security deposit stays with the lease.
On each lease there is a Primary tenant. This can be changed from the Details - Lease Information tab. 

To transfer the security deposit, you can follow these steps:

For the tenant who initially paid the security deposit, you will create a Security Deposit Application. This can be created like a Credit Note from the Transactions tab.
Then you will create an Invoice, and this can be for whatever Item you want. Typically it is done for a Pass Thru Expense type account.
Next you apply the security deposit application to that invoice.
This will reduce the security deposit liability for this tenant, so it no longer shows on their account.
It is now sitting in this pass thru account.

For the new tenant getting the security deposit, you will first create an invoice for Security Deposit.
Then you will create a Credit Note, from the Transactions tab. You will choose the Item for this Credit Note as the same as the Invoice for the other tenant - typically the Pass Thru Expense type account.
Then apply the credit note to the invoice.
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This will now show a Security Deposit balance on this new tenant.
The Pass Thru account will be back to 0.

The Bank Account will still show that original Security Deposit payment from that first primary tenant. The bank account balance is not affected at all by this transferring of the security deposit.