Re-interpret footage and maintain edit in timeline

If you're sending the edit to Resolve for color correction, select the 119.88 clips with an assumed frame rate of 23.976 and then right-click and choose Render and Replace.  This will swap the 119.88 clips for true 23.976 clips and that should meet the requirements of the matching frame rate issue that you are running into.

This should work:

Make a duplicate of your 23.976 Timeline that uses the 119.88 original clips with the assumed frame rate of 23.976. 

In the Project tab or Bin tab, set a Label Color to easily identify the 119.88 originals with assumed 23.976 (like Rose).

Import the 119.88 original clips again.

You now have frame rate from file clips (not in use yet) and assumed frame rate clips (in use).

In the Project tab or Bin tab, select a frame rate from file clip and then right-click the corresponding assumed frame rate clip in the duplicate 23.976 Timeline and chose Repalce with Clip > From Bin.  Repeat this until for each clip all have been replaced in the duplciate 23.976 Timeline.

In the duplicate 23.976 Timeline, use then Slip Tool to slip the frame rate from file clips to an In to Out that better matches how the assumed frame rate clips in the original Timeline.  Now that the clips are playing in real time, you'll have to go with a best match rather than an exact match.

In the Project tab or Bin tab, right-click one of the 119.88 clips and choose New Sequence From Clip.  Rename the resulting Sequence to match the original Timeline with something like "for Resolve" appended to the Sequence name.  There should be one clip in this Sequence.  Delete it so that this Sequence is empty.  You now have an empty Sequence running at 119.88.

Copy and paste all of the clips from the duplicate Timeline that's still 23.976 to the "for Resolve" Sequence that's 119.88 and then export XML.




In the future, try adding the 119.88 clips to the Sequence before modifying the the frame rate.  That should allow you to back out of the assumed frame rate without having to do the drawn out Replaced with Clip > From Bin when reverting to the original placement of the high frame rate clips.  Or, use Speed/Duration rather than Interpret Footage.  That's much easier to back out of.

Hello tianx etc.,
 
A better way to frame this post question might be: "How do I get my timeline into Resolve?" When you say "this is the only way that will work." you may be dismissing other options that other users may know about.
 
I can think of a couple of ways to approach this in answer to the way you have posed the question, but they are both more or less completely manual - redoing the work clip by clip.
 
But something you seem not to have considered is that if you build a timeline at ~120fps instead of ~24fps it should be exactly 1/5 as long (in duration) if you wish to represent the same number of frames. For example, a 1 second timeline at 23.976 fps will contain 24 frames. If you rebuild that timeline at 119.88fps and expect to see the same 24 frames (and no more, no less) then the timeline will be 1/5 of a second in duration.
 
I'm not sure understanding that gets you any further along towards your solution, but you might understand aspects of your problem better.
 
R.