Multiple databases per application
Please, please, allow multiple databases per application.
I think this is a must-have feature. For example, for Drupal sites, this would enable the "multisite" capability. In this configuration, multiple sites share the same Drupal core code and modules. This makes updating Drupal core and modules a snap, as you can update multiple sites in one step.
Think of a web agency that maintains dozens of Drupal sites - updating one at a time is a lot of work. Drupal doesn't support automatic updates like WordPress but it's rumoured to be available in Drupal 10. The multisite features requires multiple databases - one for each "sub-site".
Simon Richard commented
The mentioned feature is highly valuable, particularly for Drupal sites, as it enables the "multisite" capability. This capability allows multiple sites to share the same Drupal core code and modules, simplifying the updating process. For web agencies managing numerous Drupal sites, this feature significantly reduces the workload, as updating can be done in a single step. Although Drupal currently lacks automatic updates like WordPress, this functionality is anticipated to be available in Drupal 10. Implementing multisite requires separate databases for each "sub-site" within the Drupal installation.