How to change the standard period in the overview 'All websites'?

Try this URL hash with URL query. Put it manually at the end of the URL. Save the URL, maybe as a bookmark.

#?period=week

#?period=month

examples:

current week: https://demo.matomo.cloud/index.php?module=MultiSites&action=index&idSite=1&period=day&date=today#?period=week

current month: https://demo.matomo.cloud/index.php?module=MultiSites&action=index&idSite=1&period=day&date=today#?period=month

or change the URL query value:

current week: https://demo.matomo.cloud/index.php?module=MultiSites&action=index&idSite=1&period=week&date=today

current month: https://demo.matomo.cloud/index.php?module=MultiSites&action=index&idSite=1&period=month&date=today