It still unclear to me how to open a new entity in one click?
I see I can add it into a table or list as title, but that requires me to click again to open it.
Is there a way to add a button in the sidbar, or anywhere else?
This relates also to another workflow/UX question I have: how can I create a persistent custom menu at the top of the interface, which could include such button and more?
I suppose you mean how to create and then open entity view for the newly-created entity in one click.
The answer is you can’t, but in the majority of views (table, board, list, feed, etc.) you can choose which fields are visible for the entities shown, so in most cases, you can edit any newly-created entity directly in the view.
You can add action buttons to databases and then choose to have them show in most views, but a button can’t be configured to open a specific view if that’s what you need.
A button can be configured to request input from a user, so you can make a button which will take values from the user to populate the fields of a new entity.
It is not possible to add a new ‘custom menu’, but it’s perhaps worth pointing out that buttons do show up as options in the existing Actions menu.