addressed Transition without preceding clip?

[T G]

Suppose you have content on video track 1, and you want to overlay something onto video track 2 -
let's say just a simple image which is smaller than the whole screen.  An inset or insert, if you will.

The various Reveal transitions are quite useful for that, rather than having the inset just jump into view.

Is there any way to do a "one sided transition?
That is, reveal this inset image without there being an immediately preceding clip?

As a workaround, I can put a "transparent image" before the inset to transition from,
but it would useful to not have to do that.

[borate]

If this is what you have in mind, click the FADE icon at the head of the overlaid clip, and at the end if desired.

  

[T G]

Fade in applies to the entire image all at once.

Reveal is like "pulling back a curtain", as in this top-to-bottom example:
https://1drv.ms/v/s!Ak_mAiTAoy-Fgw6wFZYpCBG2GbDM

[borate]

For a true 'reveal' yours is a decent approach.

A variation would be to split the overlay near where the reveal is to be, add a zero transparency effect prior to the split, then program the transition.