I try to capture completion times by using the playthroughs feature, but find I never remember to go and update the % complete on the game itself since that requires going to the collection page and editing the game there (as far as I know). It'd be nice to allow you to update that progress from the playthrough page itself.

While debating this same problem, that I also have, I think it would be progressive to remove that completion progress from the Collection altogether, and have it replaced with the Playthrough percentage. If the game has no active playthrough, then I could see a NULL placeholder present instead. As moho_00 begins to revamp the Collection page, hopefully these things are put into consideration.

That approach would definitely handle what I'm looking for. I suppose I could just break stuff down into goals in the meantime, that does have a handy little completion meter that's shown.

Yes, that's what I'm doing as well. It's a little bit of a pain to remember to update the progress bar, but for the time being it's functional as is. The Playthroughs section will definitely be useful in keeping the progress tracker accurate.