There is no generic “merge” until you export. The most simple example:
Make a new Split of a timeline clip
Do not do anything else
Right click sub-clip 1
Choose Rejoin With Next Clip
“Rejoin” helps to reinforce the concept of reverting a split. “Contiguous” means you cannot trim the end of sub-clip 1 or the beginning of sub-clip 2, delete one of the parts, have a gap between them, or make a transition between them. As long as they are still contiguous, you can choose this at a later time without having to undo multiple things (or undo not available after reopen project).
Grouping is simple too: select multiple timeline clips, right-click one, and choose Group/Ungroup. A group is simply a saved multi-selection. When you select one member of the group, all members are selected.
This feature is awesome! I just learned about it and I’m going to use it a ton. It would be even better if there was an option to add filters to all the grouped clips. Is that something you’re planning to add?