Each result annotation found with the remote BLAST in UGENE has a qualifier that specifies ID of the sequence. The prompt way to fetch sequences of several annotations is the following: select the annotations in the Annotations Editor, open the context menu, and choose the Fetch sequences from remote database->Fetch sequences by 'id' from 'blast result' item. The following dialog will appear:

  <img src="/wiki/download/attachments/7667909/Fetching Sequences from Remote Database.png"/>

Select an output path in the dialog and click the OK button.