The Multiple Tables save option allows you to save multiple tables to the same file. If a FITS or VOTable based output format is used, this means that when the file is loaded back into TOPCAT, all the saved tables will be individually loaded in.
The list of loaded tables is shown, with a column of checkboxes on the left. By default these are selected, but you can select or unselect them by clicking. When the save is performed, only those tables with the checkbox selected will be saved.
As with the Current Table save, it is the Apparent Table in each case which is saved, so that only unhidden columns, and rows in the Current Subset will be included. On the right hand side of the table is information to remind you which row subset and ordering will be saved.