Following up on #1825, please consider adding support for {T-CONV:/Text/Type/} and {T-REPLACE-RX:/.../.../} as placeholder in fields. It's currently the feature I miss the most while switching over from KeePass.

My use-case:
Im trying to pass a base64-encoded value to a powershell script via the URL field:
cmd://cmd /C "start powershell -ExecutionPolicy ByPass -File ^"{DB_DIR}\scripts\Test.ps1^" -Base64 {T-CONV:/{USERNAME}/Base64/}"

The suggested workaround of manually converting the required value and storing it in a custom field does not work for us. We use field references (e.g. Username: {REF:U@I:46C9B1FFBD4ABC4BBB260C6190BAD20C}) and those cannot be used to retrieve custom fields.