No, you cannot access the input (output) parameter (WV*, DV*) for which the data length is set in words/ double-words by using a bit address within the user FB.
For the work area used in an FB (WF*, DF*, F*), the same area can be used in any data length (word/double-word/ bit).
Transfer the parameter for which the data length is set in words/double-word to the work area by application program in the user FB.
In the property of the user FB, you can set the size of the work area to be used.
[Related document]
For how to create user FBs, see 'Appendix 4 Procedure for Creating User FBs' in the user's manual 'Instructions' (FEH588 with index 'f' or later).