You have one text field, called Text, and a rich text field, called Body, that you want to combine into one rich text field called Body.
Create a temporary Computed text field in the form, named Body2, with the Value formula:
@Abstract([TEXTONLY]; 50000; ""; "Body");
Create a temporary Computed rich text field in the form, named Body3 with the Value formula:
Text + @If( Body2 != "Body"; @NewLine + Body2; "" );
Run an @Command([ToolsRefreshSelectedDocs])-agent on the documents you want to update. This populates the Body3 field, which contains the concatenated values of Body and Text.
Replace the Body field with contents of the temporary Body3 field with an agent:
Delete the temporary fields Body2 and Body3, and the old Text field with an agent:
FIELD Body2:=@DeleteField; FIELD Body3:=@DeleteField; FIELD Text:=@DeleteField;
Remove the fields Body2, Body3 and Text from the form. Remember that you can not show a Rich Text field in a view.