I (and I believe many others) have my videos kept in a storage server. In this way, I can keep more videos than my laptop's storage allows. When I'm not at home, I have access to them using an sshfs setup. This works pretty well, as long as the connection to my home is both efficient and stable.
On many occasions, I use Subtitle Composer to make small changes to .srt files in order to watch a video, and I don't need to use waveform feature. In other, rare cases, the changes needed are demanding, so the waveform is very useful.
When connecting through internet, just opening a subtitle file introduces great delays and huge network traffic (often paid to mobile network providers), because SC is automatically fetching the audio data in order to generate the waveform. This unnecessary behavior may also be present when opening local files on old/slow devices (due to CPU/RAM overload, in those cases). Remember: to show some parts of the video only those parts (and maybe an overhead) are fetched, while the waveform generation needs the whole audio data.
Until now, the workaround for me was to disable auto-loading of the video altogether, which is painful as it forces you to search and open the video file when needed, thus inserts a whole additional procedure. In addition, the delays caused by waveform generation come back if you really need to load the video, even when the waveform is useless at that time.
I believe that there should be an option in application's configuration, inside the "Waveform" tab, named something like "Automatically generate waveform when opening a subtitle", with the default value set to "On". When this is disabled by the user, on loading the video the waveform widget should be empty with nothing displayed except for a big button named "Generate waveform".

P.S.: I cannot decide whether this is a bug (as it creates great delays) or an enhancement (as it reduces productivity).