You have both sides of the trim selected, so this can only be a rolling trim.
You need to use P or ] to select either side of the trim (or have ‘cycle trim sides’ assigned as a shortcut to work like the U key in FCP7)
Sync lock is off by default so…
Turn sync locks on for all tracks by selecting it for the TC track – you want the / in all the buttons between the Source and Record Timeline Tracks
Now all trims will stay locked, as FCP7 is – although you may have to select extra trim points to be allowed to trim. If you turn on ‘linked selection’ this may help – but I find this only works on the simpler/stringout/assembly timelines.
There are many other ways to trim a cat…
You may want to assign, and explore, the ‘top’ and ‘tail’ shortcuts. Find your in point for your first clip in the timeline and hit ‘top’ will do the ‘mark clip’, ‘mark out’, ‘extract’ keys all at once. Repeat with ‘tail’ when you find the out of that first clip. Repeat…
Although being mouse driven, the smart tool with linked selection on is actually pretty good for trimming. I like it so much I’ve re-assigned my keyboard to be 90% left hand.
Mostly its about hours spent trimming… eventually you find the ways that work for you.
And there’s more avid folks at community.avid.com