Created attachment 161421 [details]
Checking the bug by Project Monitor.

SUMMARY

Grab Current Item, feature that possible move clip in timeline with arrow keys, despite it seem that work in UI, actually it don't move them, it is can be check when:

1. Watch the position where subtitle clip is in project monitor;
2. Save the project, restart KDEnlive (close and open) and reload the project.

STEPS TO REPRODUCE
1. Create any subtitle clip (default keyboard shortcut "Shift + S");
2. Type anything in the subtitle clip;
3. Select the subtitle clip (default keyboard shortcut "+" (plus icon) or "Shift + =");
4. Enable "Grab Current Item" (default keyboard shortcut "Shift + G");
5. Use the arrow keys to move clip in timeline to any position ;
6. After move, disable "Grab Current Item" (default keyboard shortcut "Shift + G");
7. Move the cursor/playhead in the original position subtitle and check the Project Monitor;
8. Or save the project, close, then open the KDEnlive and reload the project.

OBSERVED RESULT
Subtitle clip aren't moved with "Grab Current Item", despite the interface show it was.

EXPECTED RESULT
"Grab Current Item" should move the subtitle clip truly.

SOFTWARE/OS VERSIONS
Windows: 10.0.19045.3324
Operating System: Kubuntu 22.04
KDE Plasma Version: 5.24.7
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3

ADDITIONAL INFORMATION
I tried and Both O.S. Windows and Linux have this bug.