@Andrévan Haren I have created a project in Filemaker and already decided during the development if it, that when it would be ready, I would recreate it in Xojo. There are problems in FM that simply do not seem to be solvable, like the error message on opening that "The primary file cannot be found...", no rtf exports, no options to have the same record open in different windows without them becoming locked (are these things btw an issue in Xojo?).
Xojo is far more flexible. But you're also responsible for doing more of the work. To give an example, in FileMaker a layout is linked to a table. So you don't have to write any code to navigate, display, edit, or save records in the layout.
In Xojo you are responsible for writing the code which: creates, retrieves, updates, and deletes records from the database; maps record data to and from controls in a window or web page; and responds to user actions like clicking Save or Next. Of course that means you're not limited in the same ways as FM. You can display the same record in a hundred windows if you like. Or, when using a database server like Postgres, you can have a thousand users editing records.
Using the FM solution as starting point, I would like to keep the same design. The app has a single window with a buttonbar on top. Each button opens another layout which has its own text fields, portals buttons etc. How would this translate to Xojo?
Clicking a button in a toolbar might open a new window, at which point (Window.Open event) your code would retrieve the record(s) for that window and set the controls.
How do I create something like a FM portal in Xojo?
Xojo doesn't have the concept of a "portal" per se. You would simply retrieve related records or data and set the appropriate controls.
Is the use of Tables the same as in FM?
Yes and no. The concept of a table is common to most databases. But the specifics, such as data types, are going to vary based on the database engine you choose. It won't be as easy as FM but it will be far more flexible and powerful if you need it.
@Andrévan Haren So do I understand correctly that Xojo does not have its own build in ways of storing this kind of information and it relays on third part plugins?
You can store any kind of information you want with Xojo. But you are responsible for the code which reads and writes said information, including mapping the information to a UI or to an action which should be taken. How you store that information is also up to you: SQL database, disk file (JSON, XML, or some custom format), registry on Windows, etc. It's lower level than something like FileMaker, but as a result it's far more flexible. Third party plugins aren't necessary for your main data or for auxiliary data like preferences, though they can save you time.