Total Commander

I want to select all files in the Synchronize dialog after comparing the two directories. If I press the mouse button and hold it down in an empty space below the compared files, and move the mouse upwards to select the files, the file at the bottom of the list is not selected.

There is no "rubberband" selection at Synchronize dialog.
If you want to select multiple files using the mouse you can select them by pressing the mouse button on last file and hold it down while moving the mouse upwards or vice versa.

Either click on the last file (not the empty space below), go the other way around (from top to bottom) or press Ctrl+A.

However, I can confirm the behavior.

Regards
Dalai

2he

I want to select all files in the Synchronize dialog

You can select ALL files by pressing Ctrl+A