Question to Alpha

Hi:
Since I come from Edius, I have a fundamental question about Alpha in Resolve. I have shortened the following example prototypically to the core of my question:
1) If I define a single title in my own timeline-B (Effect > Title > Text) and then use this timeline-B in my timeline-A "as clip" (as nested timeline), then the alpha channel of the title in timeline-B is respected and a background clip (under the nested timeline) in timeline-A is visible.
2) If I superimpose two such titles in timeline-B, both title alpha channels are considered in timeline-B (and a background clip in timeline-B below is visible).
However, if I use this timeline-B (both titles only) as a nested timeline in timeline-A, then both titles are displayed, but the rest is black and a background clip is hidden in timeline-A below.
Background to my question: I would like to create a complex "title composition" in my own timeline-B in order to keep the timeline-B clearer.
// In Edius one would proceed as described above.
How do I proceed in Resolve so that a background clip remains visible under a "multiple title timeline"?
Thanks in advance - kurt
Since I come from Edius, I have a fundamental question about Alpha in Resolve. I have shortened the following example prototypically to the core of my question:
1) If I define a single title in my own timeline-B (Effect > Title > Text) and then use this timeline-B in my timeline-A "as clip" (as nested timeline), then the alpha channel of the title in timeline-B is respected and a background clip (under the nested timeline) in timeline-A is visible.
2) If I superimpose two such titles in timeline-B, both title alpha channels are considered in timeline-B (and a background clip in timeline-B below is visible).
However, if I use this timeline-B (both titles only) as a nested timeline in timeline-A, then both titles are displayed, but the rest is black and a background clip is hidden in timeline-A below.
Background to my question: I would like to create a complex "title composition" in my own timeline-B in order to keep the timeline-B clearer.
// In Edius one would proceed as described above.
How do I proceed in Resolve so that a background clip remains visible under a "multiple title timeline"?
Thanks in advance - kurt