Nothing very special about Authoring for Buttons. Use a Main Menu with several Menu Items as usual. The only thing different is that you make the main menu hot spots invisible.
Time Code Overlays
BCD's TC-100 Time Code Generator/Reader and the SB-100 Time Code Controller let you Position the Overlay Anywhere on the Screen!
TC-100 & SB-100
Overlay Styles
There are 8 Styles. The Size may be Large or Small. The Characters may
be White or Black. The Background may be White, Black, or Background Video
The Ovelay may be positioned ANYWHERE in the video using the DCOL
(Display Column) and DLIN (Display Line) commands.