Maybe there is a better way, but I can animate transparency of levels adding a FX. But before : To be able to see the all effects in the ComboViewer, don't forget to click in the Preview button (that one that looks like an eye). Without this you will not see any FX.
You have to go to "Windows" menu, "Other Windows" > "Schematic". Toggle to "Fx Mode" on bottom-right two-window Icon, the name of this windows will change to "FX Schematic". So right-click on your respective level node > Inser FX > Level Blending > Transparency. Then you will have a node between level and XSheet node. By default the "Transparency" node is set to 50%, so if everything is allright you might have you level transparent already. You can add lot of others FX with this steps, by-the-way.
So there is two ways to animate the transparency:
- Double Click on the Transparency FX Node, to show another window with the FXs options. Transparency is a very simple Fx, so there's only "Intensity" option, a numer and a slider. Change the value typing or draging the slider and you will change the transparency. Click on "Swatch Viewer" to show a small version of your canvas, click on the smalll key icon, click on next-frame icon repeatedly until your desarable frame, click again in the small key and set another value to transparency. The other way is...
- Go directly to "XSheet" tab, in the very right side of the windows might have a folder tree with "Stage", "Levels" (Col1), and FX folder. then you can click on Transparency > Intensity, and you can type values direct in the XSheet.