In 1Password 4 it was possible to insert a tab character using Ctrl+Tab. In 1Password 7 this simply moves focus to the next field, identical to pressing just the Tab key.
It's also not possible to paste a tab character in. It gets converted to a space. Oddly, all of my entries migrated from 1Password 4 have retained any tabs chars they had.
Please add this back into 1Password 7. I hadn't realised how much I used it until I couldn't!
1Password Version: 7.0.532.BETA
Extension Version: 220.127.116.11
OS Version: Win10 (1709)
Sync Type: Not Provided