Manually select and split subtitle text

Is your feature request related to a problem? Please describe.
Yes. When using the software for speech-to-subtitle conversion, long continuous speech segments (e.g. 20-30 seconds) are often turned into one single large subtitle block. This causes the subtitle to stay on screen for too long, resulting in poor reading experience and inaccurate alignment with natural speech pauses and semantic breaks.
Describe the solution you'd like
After speech-to-subtitle transcription is completed, I would like a subtitle timeline editing mode that allows users to:

Manually select and split subtitle text, then freely adjust the start and end time of each segment;
Drag subtitle blocks on the timeline to adjust their position and duration;
Provide an optional “Smart Split Suggestion” feature that recommends split points based on speech pauses, punctuation, or semantics;
Make subtitles align more precisely and naturally with the audio.

Describe alternatives you've considered

Currently, I have to export the subtitles and edit them in other software (e.g. Aegisub, Subtitle Edit), which is cumbersome and inefficient;
Some tools offer automatic sentence splitting, but the accuracy is often poor and lacks fine-tuning capability;
Recording shorter speech segments to avoid the issue is not practical for long speeches or conversations.

Additional context
This feature is especially important for educational videos, speech subtitles, interviews, documentaries, etc. Large subtitle blocks currently hurt the viewing experience significantly. Adding fine-grained post-editing capability would make the software much more professional and user-friendly. A visual timeline interface similar to professional subtitle tools would be ideal.

No files, tests, or entry points are named. Start by locating the existing subtitle transcription output and timeline UI, then determine how subtitle segments and timestamps are represented. Done should cover manual selection and splitting, timing and block repositioning, plus a usable timeline workflow; smart suggestions are described as optional.