I have a two-column LyX document. I want to add a table that will be as wide as the entire page, so that it will not have to be squeezed into a single column. I found some suggestions: table too wide for twocolumn-mode document Page-wide table in two-column mode , however, I have no idea how to implement them in LyX...
LyX knows already about that problem. Open the float settings (e.g. by right click on "float: Table" and choose "Settings...") and select "Span columns". The float will be called "float: Table*" now (note the star).
This works also for other floats (e.g. Figure).