Joshuabaksatlcs - good post; helped point me in the right direction.

For the Pro Series 2021 Schedule E worksheet, the specific box to click is in the area "check all that apply", just below the days rented at FMV entries.  Specifically it's box H, and titled "Complete taxable disposition - See Help". 

A word of caution:  if you go to the help, you will find the criteria that is needed to call this a complete taxable disposition.  In my client's case, he sold the property to a related party, which disallows claiming all the previous disallowed passive losses.  Disposition using a like kind exchange, as well as selling under an installment agreement also disallow taking the entire loss.

Regarding huge disallowed losses, my client is the "victim" of Covid policies.  He had tenants who did not pay their rent for a couple years.  Because of those policies, he couldn't evict them.  The lease had him paying all the utilities, and other expenses, as well as the mortgage, taxes, depreciation, etc.  In his case, he was also a high income taxpayer, and up disallowed passive losses were ~$65K.