Here is a sample of thumbnail screen of DMR-E100H/E200H.http://arena.nikkeibp.co.jp/news/20030714/105291/03.jpg
According to the press release in Japan, the thumbnail can be select anywhere you want to set as a thumbnail.
BTW, I think Pioneer's new coming DVDRs with HDD are designed baseed on the Japanese model - DV-77H.
Unfortunately, DV-77H can't edit out commercials on HDD programs before you transfer programs to a disc. Only you can do is making a dubbing list to edit out and transter the program from HDD to DVD-R or DVD-RW.
There is an rumour among some Japanese video philes that this restriction probably come from DV-77H's recording format on HDD. DV-77H has high speed transfer functionality, so the recording format on HDD must be DVD-Video format. That may be the reason why the DV-77H can't edit and can't record biligual audio track onto HDD like DVD+RW recorder although DVD-RW Video Recording format can do both of them.