The closest thing with the Bitcoin.com app is to tap "scan" at the bottom centre, scan your private key QR code and "sweep" it like a paper wallet i.e. withdraw your whole memo balance
But obviously this is not nearly as useful as being able to import the address as just another wallet so you can spend and recharge your memo balance with ease
That's exactly what I did and it threw out the error above. 🙁 Anyway, @memo suggested Electron Cash and it works just like a wallet, giving you the ability to spend/receive easily.
Only if you "add a wallet" then "import wallet". Don't do that. On the home screen, tap the "scan" button at the bottom middle, scan the QR code & there'll be an option to sweep.