I uninstall and install new version.
The session file format has not changed, and it does not get removed when you uninstall. I will continue to support old data formats.

The recommended way of removing sessions is clicking "delete all".

Although it is not recommended:
If you want to manually delete session data when you uninstall, delete [SessionSaverSettings] from bookmarks. There is also some data stored in cookies, I'm not sure how to delete extension cookies other than deleting the "Extension Cookies" file which removes all extension cookies.

I've released 0.13 with some major bug fixes.
Recommended to upgrade before you hit the session limit in previous releases.

You can export your bookmarks to backup your session data just in case. In a future release I hope to add easier import/export support.

I installed 0.13 without uninstalling previous version and all sessions are lost
(but that's not a problem for me)

what happens when you save a session using previous "session names"

It handles that, it just adds it to the end of the list (so you'll have two named the same).
Internally there is just an array of sessionNames and sessionUrls, it doesn't care if they are unique. When you delete, it just deletes that index from the arrays.

If you want to replace an existing one, you need to delete and re-add it (at the moment). I suppose it could ask to replace if that would be useful.

"Extensions not enabled".

What should I do? Thank you.

add --enable-extensions to your shortcut (for WinXP)

so that the shortcut properties read as

"C:\Documents and Settings\user\Local Settings\Application Data\Google\Chrome\Application\chrome.exe" --enable-extensions

It doesn't work well with latest dev 4.0201.1 ... sessions aren't saved at all.

ditto :-(
me too

but working in Chromium :-)

I updated the main post with a link to the offline installer for dev 3.0.197.11 if you want to go back.
I'll test 4.0.201.1.
Hopefully they haven't restricted the data you can store in bookmarks when they put in the sync feature.

I found the problem, looks like a permissions thing has been added. All you need to do is add
"permissions": [ "tabs", "bookmarks" ],
to the manifest.
I'll update shortly.
All my 40 sessions are still working in 4.0.201.1.

Released 0.14 that works in 4.0.201.1.