My employer sponsored NIW petition was denied after the lawyer replied a RFE notice. The USCIS' deny notice said that my employment impact is not in national scope, and I do not have much of past accomplishments. 

I want to file an appeal for my case, but it may take a long time. Can I file another I-140 petition during an appeal pending period?  

After denial of an I-140 immigrant petition, it is possible to file an appeal. This process may take a long time, since an appeal could take more than a year for a decision. While the case is on appeal, you can decide to file an I-140 petition with the USCIS in other immigrant categories, but not in the same immigrant category of the pending NIW appeal. 

If you want to file a new NIW petition when the previous NIW appeal is pending, the USCIS confirmed that the second NIW petition will not be adjudicated until the appeal is resolved. It is more prudent to withdraw the NIW appeal if you desire a faster adjudication of the newly filed NIW petition.