This dialog allows you to search for rows in the current table. It is a modeless dialog and will remain visible until either you dismiss it or you open a non-table (a query or view) in the Data Viewer. If your window manager can find space on the screen, the Find Dialog will be displayed without overlapping the sqliteman main window. You can search for the first matching row using Find First, the next matching row after the currently selected one using Find Next, or all matching rows using Find All.
The search conditions are specified similarly to the Query Builder but they are interpreted internally to sqliteman which makes it slower than running a Query Builder because the sqlite internal optimisations are not used. Also there is no column selection or ordering clause. The output from Find All looks like the output from running a Query Builder query, but it is actually the real table with all the non-matching rows hidden. Sso you can edit the rows, which you cannot do with output from the Query Builder.
Note however that making a Table Snapshot will snapshot the whole table, not just the non-hidden rows. This may change in some future version of sqliteman.