gerard,
Thank you for being persistent and giving the time code in the tutorial video. (It is not my tutorial.)
Yes, for now, you and some others will want to keep using the previous transcript workflow. To do that, just do not create source media transcripts. Use the "static transcript" option in the sequence view. Uncheck "Follow active monitor" and stay in Sequence view. The transcript, transcript tab options, and caption creation will be as before. You can work in the regular Captions and Graphics workspace or the new Text-based.
I had not noticed this new behavior of the split/merge icons until you pointed it out. At 52 seconds of the video, a section of the clip is inserted on the timeline, and it switches to the sequence view and the icons disappear. In the new workflow, when you are working with a "source media" transcript, you will always see the merge/split icons in the Transcript tab. When you are working with a "static" transcript of a SEQUENCE, you will always see the merge/split icons in the Transcript tab. If you only have source media transcript and you are in the SEQUENCE, you will NOT see the merge/split icons in the Transcript tab. To do split/merge when you have only source media transcript, return to the Source Monitor (if that clip is already open) or double click on the clip to open the source monitor, then go to the Transcript tab.
You can also uncheck the "Follow active monitor" and click on the source view, but once you get used to this, I like having it checked.
In any event, when you go back to working only with a static transcript, you will not see the split/merge icons disappear.
Stan