As suggested in your mail, I've tested the new beta 6 of 4.0 and reviewed strings, some according to the changes and some others for better comprehension (of course, I've tested the rezipped addon). French translation is ready for release.
I noticed that when I open the send later dialog, the "explanatory text" is NOT displayed in the text box (1st screenshot below)Click to view attachment
Instead, the box is empty with the cursor blinking waiting for a keystroke.
But when you leave the box empty and check a period radio button, then the text appears ( 2nd screenshot below)Click to view attachment
I think it would be more userfriendly if readable when prompt is displayed, and when you start to type in the box, the sample text gets cleared.
Just in a way to help users who discover the new version, a fortiori new users, to understand what they are expected to do. They may not realize they have a tooltip help when hovering the box.
By the way: very good improvements!
TB 13.0.1, Windows 7 64bit